The Gen 4 offers a reversable mag release which can be handy if you are a lefty. The mag release is also a bit bigger on the Gen 4 model. The Gen 4 also offers different backstraps that you can change.
The grip texture is also different on the Gen 4.
If you can find a Gen 4 handle them both and go with what feels best to you. I personally do not like the Gen 4, but everyone is different so go with what you like.
If you keep the mag release on the original side you can use any generation magazine, but if you switch it to the other side you will need the Gen 4 mags.
Trigger pull isn't a problem on either and my choice would be Gen 3 (unless you are left handed) because as the earlier poster said, it's not broke so why fix it.
[FONT="]NRA Life member.. GSSF member[/FONT][FONT="] Gunsite graduateCertified Glock armorer[/FONT]
I asked the same question on another forum I frequent. All together the the answers are mixed. Though it seems most folks lean towards the Gen. 4. I'll go by a shop one of these days and give both a feel. Though being the Gen. 3 is the only one I've shot. I'd be very disappointed if I wasn't happy with the Gen. 4. Knowing the Gen. 3 works for me, is what I lean towards. Correct me if I'm wrong because I don't have much experience with handguns, but IMO. The grip of the gun is different in your hands tell you go on range to shoot. I'd hate to make that $500 mistake...
Let me ask you this, what is pushing you toward a gen 4? Is it because it's the latest and greatest, or maybe you think it will be worth a little more down the road. If you like the gen 3 just get it, they don't get any better. If it feels good to you it is the best one.
Most of the problems with the Gen4 extraction did not apply to the little subcompacts in the first place. Anyway, they've been resolved. Feel free to buy whichever feels better without reliability concerns.
My preference is the Gen 3, have both a 19 and 26. The one thing I do like about the gen 4 is the enlarged mag release. I wasn't a fan of the new texture on the grip though. Recommend handling them both and get what's best for you.