What would you guys use if you were shooting in a competition.
Depends on the competition.
If you are shooting 3-Gun, USPSA Action pistol, Rock-Your-Glock, or Steel Challenge, basic cheap Federal or Winchester 115 gr FMJ from Walmart is just fine. (Some people have feeding problems with the relatively-weaker Federal ammo. I haven't, and that is through 2 G19s, a G34, 3 Gen 4 G17s, and a 5" XD9. But yours might.)
If, on the other hand, you are shooting some variant on bullseye, then you are probably going to want something a bit more specific to your firearm, and should get into reloading.
(Granted, if you are shooting
any competition a lot, you'll want to get into reloading, not only to match a good load to your gun, but you'll be able to shoot quite a bit more for the same amount of money.)
I
would suggest that you buy a box of each of the cheapest types of ammo you can find, and spend a day at the range on a sandbag, checking their accuracy out to at least 25 yards. (40-50 is fun, too). Most will probably be similar, but there may be one that just is very accurate out of your particular gun---though most likely, any one of them would work fine. And there may be one that your gun just doesn't like. Spending $45 to check the cheapest 4 ammo brands is going to be worth it.
Look for feeding problems, and check for accuracy. If they all feed and give acceptable accuracy at the ranges you need, buy the cheapest.