I've had a KJW M9 for about 2 years now and I have been very pleased with it.
It's seen a LOT of use in that time, and admittedly poor maintenance in the first year, and I have had 0 failures.
The mags have failed due to mistreatment by a friend (never lend out a GBB), but all were easily repairable.
I love Berettas, so I am heavily biased. That being said, the ergonomics seem to be squared up nicely for most human beings.
Some people find them chunky because of the width of the double-stack magazine, but where I have large palms and short fingers I think M9s are just dandy. 1911s are largely unusable by me for the same reason
.
What Slide said about trying some out is absolutely critical.
These are functionally good guns, and I would have no problem recommending them.
Your best bet, however, is to get
Age Verified so that you can check out the restricted sections of this website and see what else is available.
Once you've done that, do some serious research before you buy into a GBB system.
An airsoft sidearm may be cheap on it's own, but they quickly become expensive.
Mags are ~$50 a piece.
A propane adapter is ~$30.
A belt/ shoulder holster/ whatever is ~$30-$60.
Silicone-based oil ~$10.
Proper maintenance is weekly.
You need a 'float' budget of about $100 in case the sky falls and you need to go out and play but all your mags are busted and you need 2 more.
Once you've factored all of this in, the saving you get when buying a less expensive system like a KJW doesn't seem so big, since the extra costs associated with a GBB pistol are pretty much the same no matter what you get.