I hate to just join the crowd, but I like the Browning HiPower. As they come, they are not perfect, but the problems are fixable. I like to think of them as being 90-95% there. But that is about the best I can say for most guns.
The triggers usually need some help, but some actually are pretty good. I find they vary a lot, and if you can check several, you can usually find one that is at least decent. Better than a DA auto trigger to me at least.
The hammer might bite, and different people get bit more by one hammer type than the other, but that's easily fixed too. The regular spur hammer with a couple of serrations filed away works for me.
Grips make a big difference. Thinner ones feel great to most people, and thick ones like the Pachmayr steel belted radials feel good to others. The basic frame shape seems to feel good to most people. It's just a matter of how thin or plump you want it.
Yeah, it's too bad these things need done, but the point is, they are fixable.
I can get guns that might have better triggers, but no matter what I do or spend they won't carry IWB as comfortably as the slim, rounded HiPower slide and frame.
I can get a gun that doesn't bite my hand when I shoot it, but while I can correct that on a HiPower in a few minutes with a file, I'll never be able to make another gun's grip frame feel as good as the Brownings.
Another one I like is the S&W 3913. I always liked single stack medium size 9mms, and tried most of them. I've had a couple, and like them a lot (even if they are DA). They are small enough to carry well, yet big enough to shoot OK.
But my favorite mid-size 9mm is the HK P7. I love those. I have two, and they bumped the 3913 out for my choice of mid-size 9mm. They are flat enough to carry easy, and I can shoot them better than any gun I have. I shoot them less than some other guns, but even when I don't shoot a P7 for awhile, I can pick one up and do better with it than what I've been shooting. It's as close to fully ambidextrous as any gun I can think of, and I shoot it better "wrong handed" than any other pistol.
There are a lot of gripes about the P7, but often they are exaggerations at best. They get hot due to the gas system after about 50 rounds, but some will act like you can't get through a magazine without setting your hand on fire.
Others swear that if you don't carry a P7 every single day, you will forget how to operate the thing. You take a firing grip, squeeze-cocking it in the process, and shoot. I've let quite a few people shoot mine who have never seen one before. Many have shot it again months later, and even though I keep quiet and watch for it, they had no trouble remembering how it works.
I got a Sig P-210 a couple of years ago. Actually, it's a Danish contract M/49. It is a wonderful gun, but I hesitate to say it's the finest 9mm.
The hammer chews me up worse than any gun I've ever shot. It could be fixed however, and there are "bolt-on" beavertails out there.
The magazine catch is the Euro type, which is not terrible, but not exactly handy either.
It's a pretty big gun for an 8+1 9mm. Nice for shooting, and the balance lets it "hang" nicely, but it's a bit big for what it is.
The safety lever is tough to reach with the right thumb. I can do it by shifting the gun in my hand, but that is not what I'd prefer by any means. It's easiest to manipulate it with the left hand, but I want a carry gun to be operable one-handed.
Magazines are over a hundred bucks when I see them. Usually around $140.
Most of these things are fixable, but finding someone (there are a couple) to do it, and (mostly) paying the price, is no small thing.
But the P-210 is soooo smooth, and it shoots so well! Just working the slide makes me smile. With the recoil spring and barrel removed and the hammer cocked, I can tilt the muzzle just a little bit and the slide comes sliding back.
The trigger is a joy. It's a two stage, similar to military rifles, but much better feeling. It's hard to describe. You have to feel it to understand completely.
It's fun just to sit and study the inside because it's so well finished in there.
And I am always surprised at what it feeds. It was designed long before 9mm JHP ammo was common, and it accordingly looks like it was designed around FMJ with a feedramp that is as close to vertical as any I've seen. Yet it gobbles up everything I've tried. I have some plated JHPs that are terrible feeders, choking everything but the P7s, and the 210 feeds them without a stutter. I shot a lot of cast SWCs in 9mm last year, in three or four designs, and it ate them up.
And everything shoots into neat little groups. Almost every load shoots better groups in the P-210 than any other gun I have tried it in.
Overall, as a range gun, the P-210 is incredible. But it's way down the list of guns that I'd carry. And it's not because of money, because I'll carry what I think I can shoot and operate the best whether it's my cheapest gun or most expensive.
So I can't say it's the best.
But it is the best 9mm range gun I've shot, without question.