There's more choices right now than ever before(including all the old choices still around).
For a doityourselfer or someone willing to have an airsmith work on your gun, the generic BB's(BlowBacks) are a good choice. These would be(deep breath) The G1+,G2+, WSP, PTX, G1, ZX, G2, ACP, ACP2.0, Overlord, T68, Delta68, Etc.
The weak point in all these guns is the piercing mechanisms for co2. I have converted most of these guns including my own Miltecs, Armotechs and warsensors as well as a PTX and a delta68 to use the pierce pins from the CCI Phantom pumpgun. These CCI pins outlast all others currently available by a clean 10 to 1 and are $6.00 each!!!
This will turn these pistols into dependable shooters.
Polishing the barrel, by whatever method you prefer(I use polishing flexhones) will really make these pistols shine.
For a primary this is my choice, understand that I shoot a ridiculous amount of paint by most pistol people's standards because I play in large class open play. Last weekend at Hell Survivors, there were 80some folks in open play.
Because several of the Mercenaries(A home team that can be 'rented' by the highest bidders in the big games, the Mercs are TOUGH and with their Eclipse sponsorship are running all Egos) and several of us regulars wanted to play together the refs set the teams at 30-50 and I ended up shooting 450rds in 4, 15min games through my Miltec G2 alone. Good Times!!
For out of the box fun(with only the quickchange adapters for the mags) the TAG8 can't be beat, though.
You can just buy it, 3 mags with adapters and a holster and you're ready to rock! This gun normally rides as my sidearm to my Miltec pistol.
If you're going to wear the gun holstered for any period, especially during daylong scenario play, this is the gun, as the BBs magazines end up vertical in the holster, the paint compresses as you run and the spring will not let it return to shape. The mag of the TAG rides parallel to the ground and is much kinder to your paint.
The TAG cannot maintain the rate of fire of the BBs even if you have the supply of mags and has some shootdown(vel drop) in rapid fire.
A Palmer Stroker is more in initial outlay, but worth it in the long run over a TAG8, if you're really going to use it as a primary.
In rapid fire and general ease of use in longer play the stroker rules over the TAG, but it's big and heavy if you carry it alot holstered. The fact that they use inexpensive 10rd tubes to load makes them cheaper than a TAG with 6 mags(a friend of mine runs with that many).
They can be made just about any way you want!
I guess my best advice is that you will have to try the different styles for yourself to really know. Borrowing different pistols to use is the best way to go, because many folks are turned off of pistol play because the choice of pistol they started with was the wrong one for them.
We play Pistol and we encourage the Few despite the discouragement of the Many.