If you looking at the glock or kahr I think you are looking at the ultra compact guns, the glock is good so is the Kahr. I would also include Springfield in the mix. The glock is a good gun, not accurate as I like, springfield is good also but again not as accurate as I like. The reasons glock are so popular with LEO comunity is the cheep price and simple to maintain. Forget the Bersa.

Decide on the size gun you want first, don't focus on the name. I carry Sig or a Wilson Combatcustom 1911. I do love the Glock 19 though, if I were looking for a one gun on a budget that would be it.