Life Inc. - We love Whole Foods but shop at Wal-Mart John Gress / Reuters A worker walks through a new Wal-Mart store in Chicago in this January 2012 file photo. Wal-Mart got low ranks in a Consumer Reports survey of favorite grocery stores. When it comes to grocery shopping, people say they value customer service and fast checkout lanes. But these days shoppers often choose their grocer based on two things, experts say: Price and convenience. That may be why Wal-Mart is the nation's No. 1 grocer, even though it ranks among the least-beloved store chains. "People who like Wal-Mart shop there, and people who don't like Wal-Mart shop there more," said supermarket consultant David J. Livingston. Livingston said people who live in a big city like Chicago might place a higher value on a convenient location because they're more likely to have to lug their groceries home by hand, or at least battle traffic and parking considerations. For people who live in very drivable communities, low prices are likely to be a primary consideration, Livingston said. That's one reason he said stores like Wal-Mart, Aldi and Target are attracting customers who may have previously shopped at more traditional grocery stores, like Safeway or Albertsons. On Tuesday, Life Inc. asked readers what bothers them most about grocery stores. More than 50,000 readers responded to our survey, and although many said they don't like dirty stores and long lines, the most common gripe was high prices. Many of our readers admitted they grudgingly shop based on price. "Love Trader Joe's, Co-op, Whole Foods, etc. but low price comes first," one reader wrote. Luv/Hate with Walmart. We are disabled and on a fixed income -- go to Walmart for prices but hate the store," another reader commented. The poll accompanied a story about Consumer Reports" latest survey on the best and worst supermarkets. The consumer magazine's readers gave the highest marks to stores including Wegmans, Trader Joe's and Publix. Wal-Mart, the nation's largest retailer, ranked low overall but got excellent marks for price. The company itself also recently cited low prices on brand-name groceries and beverages as one of the key reasons sales have increased. Wal-Mart spokeswoman Sarah Spencer said the company surveys about half a million customers each month and finds customers generally pleased with the shopping experience. "Our priority is ... to focus on our customer and give them what they want, which is low prices, a broad assortment (and) great customer service," she said. Livingston, the supermarket consultant, said addressing other customer complaints could literally come at the cost of their key advantage. " (Wal-Mart's) only appeal is price, and yeah, they do have a lot of shortcomings, but for them to correct those shortcomings, that would cost money," he said. That's particularly true now, with the economy still relatively weak and food prices on the rise. More than four in 10 respondents told Consumer Reports they had switched supermarkets because of high prices. "We switched over to Aldi," one Life Inc. reader wrote, referring to a chain with more than 1,000 outlets, mainly in the Eastern U.S. No name brands, but we save a ton. I love Wegman's, but we don't have them here and Publix is just too expensive. Still, for some Life Inc. readers low prices weren't enough to sacrifice other things, like well-stocked shelves. I recently switched from Wal-Mart to Kroger despite the higher prices. I love going to the grocery store knowing they will have what I need," one reader wrote. Only about 13 percent of our readers said a lack of fresh produce or meat is their top concern. Livingston said those shoppers who do value quality over everything else may also be abandoning the traditional grocery chains in favor of more high-end stores. Whole Foods, known for its fresh and health-conscious items, also has seen strong sales improvements recently. Some readers said they can't settle on just one store. It's very hard to find a one-stop-shop kind of place anymore. I end up splitting my shopping between three or four different stores just to try and get the best balance between quality and prices," one reader wrote.