As someone with some winforms and client applications experience - is it worth going back and learning the way traditional ASP .NET pages work, or is it okay with moving str
Here is the great thing about MVC. It works closer to the base of the framework than normal ASP.NET Web Forms. So by using MVC and understanding it, you will have a better understanding of how WebForms work. The problem with WebForms is there is a lot of magic and about 6 years of trying to make the Web work like Windows Forms, so you have the control tree hierarchy and everything translated to the Web. With MVC you get the core with out the WinForm influence.
So start with MVC, and you will easily be able to move in to WebForms if needed.
I agree with Nick: MVC is much closer to the real web paradigm and by using it you'll be confronted with how your website really works. WebForms astracts most of these things away from you and, coming from a PHP background, I found it really anti-intuitive.
I suggest you directly jump to MVC and skip WebForms. As said, you'll be able to get back to it if needed.