Well, I've learned to love the colt. I use it as a backup to the m4 when the firing rate isn't fast enough. The trick is counting the rounds. If you know you're out of bullets, you can just dodge away and reload. It's great for spar too, but again counting is essential. I've beaten some good sparrers recently with my colt. It's got such low freeze after the shot, you can almost weave in front of a bullet, get off a shot and then dodge. It's great. Be warned, the reload is a killer.

The Glock seems to be a decent choice recently, since it was improved. It's cheap and has good spar capabilities.

Anyway, you want to think about balancing out your arsenal. I picked the Pbp to balance my m4. The colt was bought as a novelty really, but it's become one of my favorite guns. Surely underrated if you can use it properly.