BB guns are less accurate and less powerful (Smoothbore with a spherical projectile) but far more fun than pellet shooters (Which I think are all a bit naff, just my opinion though, certainly not fact).

I like to think of currently available pistols like this :

If you want accurate shooting you get a SSP, PCP or Springer.

If you want awesome realistic fun you get a BB gun.

If you want a compromise get a CO2 Multishot.

Again, just my opinion, I cannot stand the revolver inside an automatic principle, even when Umarex make revolvers they stuff it up by having a largely moulded cylinder.

When Umarex make pellet shooters that don't use an internal revolving cylinder I'll be the first in the queue.

Finally, and people will be getting sick of me advising this, have a look at a Cybergun Witness 1911. Its BB gun and therefore not too accurate but when you pick it up you will buy it.