I am in the camp of preferring the original 5150 or even the 5152. The 3 is less aggressive and a hell of a lot more polished sounding (in a not good way imo.) I like the originals raw aggressive nature. It is just more in your face and a bit darker. They both have a similar base sound, loads of mids even with them turned down, etc etc. It is definitely something you have to hear to understand fully.
How ever, I have to say that the clean channel rules (it is made by fender after all) and the crunch channel is pretty awesome also. I like the crunch on the peavey versions also. I have to say though, unless you really need that pristine clean sound you are better off getting one of the peavey versions for price alone.
The cabs on the other hand are phenomenal! I'd buy one of those in a heart beat if I had the cash.