I'm not going to argue about whether it's the best for gameplay, but the range for the shotgun is more realistic than shotguns in most other games. Here's a chart I found for shotgun spreads at different chokes:
http://www.wildfowlmag.com/tips_strategies/shotgun_062304/
(Scroll down for the first chart)
Even with the widest spread choke, 80% of the pellets end up with a 30" diameter circle at 20 yards. That's even farther than what it is in KZ2.
With a narrow choke, you could fire a shotgun at 40 yards and get 70% within that same circle.