I have BFD2 & BFD3 installed on both of my systems.
I confess that I find BFD2 a lot more intuitive than BFD3, although this is probably due to 2 reasons:
1 - I haven't yet sat down with the BFD3 manual and read the bits I need to read
2 - There are a LOT more options regarding routing/ambient channels which makes (for me) the mixer page rather daunting.
Having said that, there's no discernible difference in sound quality and BFD3 comes with kits which you can't load up in BFD2. BFD3 of course loads all of the expansion packs from BFD2 and all earlier versions.