I have flown only the b2.
I am quite sure the 407 is faster and probably a bit smoother.
The b3 i am sure has more power especially at altitude and hot temps.
The 407 in standard config has probably more room for baggage. The b2 or b3 have the option of the squirrel cheeks that add more room to the heli since the tail (or rear) baggage compartement is not quite big.
I am also quite sure the b3 has a higher fuel consumtion than the 407 and maybe the 407 uses abouz the same amount of fuel than the b2.
Cheers
bitmonx