Exclusive: Stirling prize shortlist revealed Simple. Restrained. Simple and restrained. Possibly also sober, plain and very much not iconic. This year's RIBA Stirling prize shortlist reflects the zeitgeist of our straitened times, with their mistrust of extravagance and waste, more than any previous. Architects such as David Chipperfield, Stanton Williams and O'Donnell + Tuomey, who never knowingly overdecorate, feature prominently. Rem Koolhaas's practice, OMA, better known for its amazing cantilevers and improbable collisions of form, offers as its two shortlisted projects assemblies of intelligently arranged boxes. Even the Olympic Stadium, usually an occasion for rhetorical displays of national pride, is notable for what it leaves out and what it is not - it is not the Beijing bird's nest and uses considerably less steel than its Chinese predecessor. Zaha Hadid, victorious for the last two years and not much interested in restraint, is absent. Her most likely contender, the Olympic Aquatic Centre, was not entered, probably so that it can be submitted in another year when the ungainly wings containing temporary seating - widely agreed to be the building's worst feature - are removed. None of which means that all the projects are necessarily cheap. The stadium, for one, is not. Nor that they are insipid. Chipperfield's Hepworth Gallery has a rock-like obduracy that is anything but. But they are all works that avoid the sugar rush of instant spectacle and which, by holding back a little, help you better experience the arts, drama, landscape or sport in and around them. The judges, led by the architect and former Royal Academy president Sir Nicholas Grimshaw, will have one or two big decisions. The first is whether to give it to the stadium, which is by far the largest and most significant project - in terms of the worldwide attention it will draw - on the list. It is a handsome thing, hard to ignore, with the interesting idea that it can be partly dismantled after the Games, so as to avoid being the usual post-Olympic white elephant. Even if, due to political complications, this possibility is unlikely to fully exploited. The judges may want to recognise the Olympics in some way, and make up for the failure last year to award the prize to the much-admired Velodrome. If not the stadium, they will have to decide which is the best of the other five simple-and-restrained projects. A bank tower? Ummm, not very now. A Maggie's Cancer Centre? Like the Oscars, the Stirling prize can be attracted to serious illness, so much so that they awarded another Maggie's the prize a few years ago, but they may not feel like repeating themselves. The judges should, of course, be swayed not at all by questions such as who and what has won before, and whether a bank, a stadium or a refuge for cancer sufferers would make the architectural profession look more lovable. They should simply decide which is the best building. Here, the decision is a tight one, as there are no real turkeys on the list and both the Hepworth Gallery and the Maggie's Centre, for example, do nice things in relating the inner life of the buildings to their surroundings. My choice would be the Lyric theatre in Belfast, a view slightly tinged by the feeling that it would be good to look beyond the usual names and places, but mostly driven by the belief that its arrangement of materials and space, in the service of the building's purpose, are as good as anybody's. But, in an outstandingly sane year, when there are no outrageous exclusions or inclusions, any of the others would also be a good choice. My bet is that it will come down to the stadium versus Chipperfield, with the stadium winning. The RIBA Stirling prize will be awarded on 13 October 2012 Olympic Stadium, London. 2012 Olympic Stadium, London Populous Odds 5/1 The Olympic stadium got some sniffy reviews when its design was unveiled five years ago - too plain, too ordinary was the general view. Now, plainness, simplicity and its economical use of steel are seen as virtues, as is the fact that it is partly demountable. In theory at least, this should make it easier to reuse after the Games. It is also a handsome, confident-looking structure. The only problems are that its price was not quite as plain and ordinary as its appearance implies, while protracted struggles to find a new use after the Games suggest that it is not as adaptable as all that. These struggles are probably more to do with politics than design, however. Previous form (as HOK Sport, Populous's former name): Arsenal's Emirates Stadium and sliding roof over Centre Court at Wimbledon. Maggie's centre, Gartnavel, Glasgow. Photograph: Philippe Ruault Maggie's centre, Gartnavel, Glasgow OMA Odds: 9/2 With its other shortlisted project, OMA shows it can do nice. This is one of the series of Maggie's cancer centres, where leading architects design places where patients and their relatives can come for advice, counselling, company or simply peace and quiet. They were conceived by the architecture critic Charles Jencks and his wife, Maggie Keswick, who died of cancer, as antidotes to the architecturally depressing spaces in which most treatment takes place. OMA's centre is less assertive than previous centres such as Zaha Hadid's in Fife, or the Richard Rogers-designed building in London that won the Stirling in 2009. Instead, it focuses attention on the landscaping, which is designed by Jencks's and Keswick's daughter, Lily. New Court, Rothschild Bank, London. New Court, Rothschild Bank, London OMA (with Allies & Morrison and Pringle Brandon) Odds: 4/1 Given that bankers are only slightly more popular than child-abusers, it would take some nerve by the Stirling judges to give this first prize, even though Rothschild likes to protest its difference from the casino banks of ill repute. On architectural merit alone, it is a contender: it seeks to create the headquarters for a powerful financial institution, while also offering the world outside an arresting open space off a narrow City of London street. It is intricate and sometimes playful, even if not entirely politically correct. OMA is the practice founded by Rem Koolhaas, which, despite international renown, has not troubled the Stirling judges until now. Previous form: Central China TV HQ, Beijing; Seattle Central Library The Sainsbury Laboratory, Cambridge. The Sainsbury Laboratory, Cambridge Stanton Williams Odds: 7/2 A place where "world-leading" scientists can study plants in the setting of the University of Cambridge Botanic Garden. As well as fulfilling taxing technical demands, the architects Stanton Williams aimed to achieve a "collegial" environment conducive to the sharing of ideas and knowledge. The result is an L-shape, like two sides of a cloister or a college court, that is also open to the landscape. The architectural approach is rectilinear, well-built, with sharp, straight lines offsetting the natural surroundings. The structure has a certain solidity, while also creating a series of layers through which light and views are filtered. Previous form: University of the Arts, King's Cross; Tower Hill Square (public space next to Tower of London) Lyric Theatre, Belfast. Photograph: Dennis Gilbert/View Pictures Lyric Theatre, Belfast O'Donnell + Tuomey Odds: 4/1 A beautifully considered and well-made theatre by the Dublin-based O'Donnell + Tuomey, who were shortlisted last year for their An Gaeláras cultural centre in Derry. The design is about progressing from the city outside through the foyers and bars to the performance space at the heart of the building, with views to a river and greenery. It uses a lot of brick and timber, but avoids the worthiness that sometimes goes with these materials. Belfast doesn't always make headlines for its architectural quality and its new Titanic museum is a contender for the Carbuncle Cup - Building Design magazine's prize for the year's worst building. But the Lyric is on the Stirling list on merit. Previous form: National Photographic Archive, Dublin; Photographers' Gallery London The Hepworth, Wakefield. Photograph: Iwan Baan The Hepworth, Wakefield David Chipperfield Architects Odds: 3/1 A sober, impressive art gallery named after the Wakefield-born sculptor Barbara Hepworth. It is designed by David Chipperfield, who has several Stirling near-misses to his name and one win, in 2007. His strengths are the attention he pays to light, space and material, but the judges usually end up going for something more spectacular or else for projects that are seen to have more social significance, such as schools or housing. Set next to water and to historic industrial buildings, the Hepworth seeks to address its site and emulate their Yorkshire toughness with a structure of pigmented concrete. Previous form: Neues Museum, Berlin (shortlisted for Stirling in 2010); Museum of Modern Literature, Marbach, Germany (winner 2007)