Yes, this is certainly a duplicate question, but I wanted to get some fresh takes.

My impression is that Telerik is a much more complete suite, but I'm really really turned off by the responsiveness of their controls. It just seems "clunky" in terms of responsiveness (I have a very fast computer and video card). Scrolling in a grid and transitions chunk, even in their latest demos where they claim to have good performance. I do like that their WPF suite matches their SL one in terms of API.

Infragistics has fewer controls and less theming possibilities, but their controls are very responsive. Scrolling in a grid is fluid, as are their combo menus and all the other controls.

I checked out ComponentOne and their controls seem analogous to Telerik's in terms of the points mentioned above but are a little less "pretty".

Any thoughts from other users of these suites? Basically, what I'm looking for is a suite that will be highly performant and responsive, relatively customizable from a theming standpoint, and have enough functionality to develop a LOB SL application without having to use multiple suites to satisfy the majority of common requirements.