3X seems to be more popular than 2X, but both will do.
Chicago Pneumatic (no relation to Harbor Freight's Chicago whatever) is the standard and most of what you find out there will be a clone of a CP. And just because they are clones does not mean they aren't as good as a CP. Avery's guns are copies of the CP and parts interchange, according to Bob. Ingersoll Rand also makes a good gun, but they have their own numbering system and an ACV12 won't be exactly comparable to a 3X--it will actually hit a little harder & slower.
Although I prefer my IR gun over my CP, the CP, being a little shorter fits into tight spots better and there was one spot on my wings where I could not use my IR, but the CP worked.
New CP & IR guns are spendy, so if you want one, buy it on Ebay.
Sioux guns are popular but I haven't used one so I can't comment.
My old ATS gun was a piece of junk but I understand new ones are better.
I am not impressed with the Taylor, but the owners of the Taylor's I have tried have been satisfied.
My own preference is my very used IR ACV12 which I bought thru Ebay for $35. Very controllable, hits hard or easy depending on air pressure.
There are a couple dozen guns on Ebay right now; be sure to check out the sellers and know what you are bidding on if you go with Ebay.
Lastly, note that most folks will recommend what they own and are satisfied with, which may be the only gun they have used. Try out several different guns if you can.
