I'm partial to the 3-bolt necks, 'cause I've set up mine before when the micro-tilt helped get the last bit of adjustment needed.
I think G & L went to the 4-bolt necks due to lingering impressions of the 70's 3-bolt Fenders.
that said, the new ones I pick up play just as nicely.
One thing - I have small hands. The standard nut width is 1 5/8". Some players are more comfortable with the 1 11/16" width, like on Fenders.
Joneser's right about the fact that there are a lot of neck options, although most G & L's up till a few years ago were standard orders.
That's another nice thing about the G & L's - you can go to a dealer and custom order one fairly easily by picking a few options, like those gun oil tint necks that joneser likes - they look awesome!
It's kind of like a hot rod shop in that way. G & L's finishes are excellent - their bursts are beautiful, and more consistent than some other companies. (I see a lot of bursts that just look off to me.)
I see plenty of nice used G & L's in the $500 - $650 range, depending on the model and features.