Does anyone have any recommendations for either of these validation ASP.Net MVC Validation frameworks?
xVal is pretty much the standard way to do client-side validation in ASP.NET MVC. Actually today Steve Sanderson just released a new version of it :)
The ASP.NET MVC v2 will have client-side validation built in, but it is currently only in Preview 1 so it will be quite some time before that project will be released. You can view more about this on Stephen Walther's blog post...
Microsoft Ajax CDN and the jQuery Validation Library
I would suggest to use xVal until ASP.NET MVC v2 get released.
I'm using XVal as you get client and server validation with the same framework, it integrates well with MVC code.
I've been using the Data Annotation Validators with great success. I know it's not the final solution that we'll see with MVC v2, but it's easy to implement and very flexible.
http://mstecharchitect.blogspot.com/2009/08/data-annotations-validation-in-aspnet.html http://www.asp.net/learn/mvc/tutorial-39-cs.aspx
The advantage to this approach is that you can do some very complex validations (albeit not client-side) through creating custom attributes. It's also very testable.