1. You are very fortunate to belong to a dept that allows you to chose your duty weapon. Take advantage of this if you don't like the issued weapon. If the issued weapon is fine, go with it. That will be anything between $400-600 in your pocket, which you can use for other things. Like ammo. Or a vest. Or a BUG.
2. 'Pretty' should not be one of your search criteria. Pretty is as pretty does. This is a duty gun, not a look-cool gun.
3. Go with the one you shoot best. Caliber wars are stupid. If you shoot a 9mm like a pro and shoot a .45 with less accuracy, go with the 9mm.
4. Light rails are a GOOD THING. I'm convinced that anyone who thinks they're hyped tactical BS has never done a no-light scenario with a flashlight (as opposed to just lining up and shooting targets in the dark). Oh you have? Great. How many times did you reload? If you managed to keep your gun on target, the target illuminated and got your weapon reloaded quickly, I wanna know where you had your third arm installed.
One of the lights (M3?) has a belt clip where you can keep it on your belt and use it as a handheld flashlight, and then clip it on your sidearm in about 1 second. Me, personally? I'd leave it on the gun 24/7 and carry a maglight on my belt. Best of both worlds.
5. This is important. Take in all of the firearm advice from your fellow LEOs with a nod and a smile. And then chuck it into the dumpster until you can figure out who knows their arse from a rabbit hole and who is prone to telling tall tales. Many cops are not shooters, and all cops like to tell war stories. And no war story is better then the bulletproof suspect, who shrugged of 30 rounds of X and eventually succumed to being shot in the pinky with one round of Y. The close 2nd-place story is how Gun Z always runs but gun W is a jammomatic. Coming in third is how Ultra Black Ninja ammo will blow a hole in a suspect's chest a foot in diameter, but Mega Super Tactical ammo just bounces off.
6. Practice.
7. Practice.
8. Practice.
9. Practice.
10. Practice.