Q:

ExtJS or SmartClient?

I would like your opinion about these two frameworks. I like a lot the features of ExtJS, but recently I saw SmartClient and it seems to be great too, and free (its Client side features) for commercial projects. I tried a little of SmartClient and it seems to be easier than ExtJS, and it has a better documentation tnan ExtJS.
BUT.. I didn't work with any of these frameworks and maybe I'm wrong. That's why I would like the opinion of people who has worked with them.
And BTW.. how does the license of ExtJS work? you've to but one license for each developer and then you're able to develop and sell every app you want or you have to buy a license for each app you sell?
Thanks in advance for your help.

A:

This has been pretty well covered on SO.  Specifically here and here.
Ext JS is licensed per developer not per app.  
I'm an Ext JS developer so I'm partial to Ext, but I have no opinion of SmartClient good or bad.  If licensing is the most important criterion SmartClient might be better for you.  If you want to weight the technical merits see the links above, or even better evaluate them both based on your own needs.

A:

I use SmartClient and am quite happy with it and the support provided by Isomorphic. The U/I widgets aren't the nicest out there, but you can see that they've been around for some time by the richness of their API.
It's also quite easy to roll out your own custom controls when the built-in ones don't suit your needs. For example, we integrated Raphael pie chart SVG drawings inside custom Isomorphic canvas classes. We also integrated Mondrian/JPivot analytical technologies which are legacy JSP pages, using Smartclient's HtmlFlow control. It's quite powerful what can be achieved.
One thing I regret about Smartclient versus other technologies such as jQuery, is a clearer separation between the work a web designer does versus the work a developer/programmer does.
With Smartclient, it's mostly done thru code, even the layout of components. There's no HTML per say. They've separated very well the skinning (css), but that's about it. Everything else needs to be done by a developer/programmer thru Javascript code. Smartclient is good for single-page apps.
I can't speak for ExtJS as I haven't used it real production environments, but in the end I think it all boils down to the licensing model and programing/design model you want to be using.

