Competition Shooting
In both IDPA and IPSC competitions, you can only shoot 6 rounds from a revolver and then you must reload. 7 and 8 shot revolvers are legal, but you are suppossed to load only 6 rounds.
If you want the gun for fun, CCW, protection or whatever, then the 7 or 8 round is probably a good choice. If you want the gun for competition, you might want to think about the 6 shooters.