What are you using it for?
If you're just target shooting, then whatever 9mm feels best in your hand would be the least expensive to shoot.
If you're hiking and camping the Colorado mountains and want to stop a wild animal from eating you or your family, then I would suggest a .45 with a lot of capacity, but still somewhat compact. Like maybe an XD45 with 13+1 capacity.
If you mountain bike or dirt bike the mountains and want a comfortable defense weapon to carry under moto gear, I would suggest an XD-S 45 because it is extremely compact, very slim/light, and you can still carry 10 rounds of .45 plus another mag or three in a pocket or pack. Or a Sig Sauer SC maybe, if you want to spend a bit more.
If you want home defense, any .45 will do. Or maybe an nice shotgun or AR. I have a tac light and night sights on my home defense .45 pistol, and a tac light/laser on my home defense Sig M4 rifle. Some people will imply that you need to chose one over the other (tac light-vs-night sights-vs-lasers. But in a home defense weapon, there could be a benefit to all of them in certain situations.
I used to think there was one single weapon that could fulfill all of my needs, but I ended up with several pistols and rifles.
If I had to chose a setup to carry into urban combat when Obama sends the New World Order troops, I would probably strap my XD45 pistol to my side, sling my M4 rifle around my chest, fill my backpack with a fuckload of ammo, eat a couple of peanut buttery poptarts, hop on my KTM Enduro, and GTFO!