Having owned both framed and frameless boats I agree wholeheartedly with what sldrose just said. Further to his comments above I can tell you that I find frameless boats much, much easier to kick and control with fins. Sitting lower in the water puts more of your legs in the water and lets you kick and control with fins much more efficiently. Now that I've gone frameless I would not go back.
I gave up floating the bow out of a framed pontoon as I found it way too hard to effectively control while trying to fish. I find the smaller, more maneuverable frameless boat makes controlling the drift much more manageable.