I've used Colt kits before, but I don't think they're worth a premium over some of the other reputable brands that I suggested. IMO, LPKs are more of a threshold product. You are getting basically the same GI trigger, same A2 grip, same detents, and same springs. Minimum cost parts that are in spec are the way to go - you get accuracy from a better barrel, better trigger, and performance from a quality BCG. If you're buying based on brand, just buy the whole darn rifle.
^^^THIS^^^The LPK's are either in spec or not; just saying. CMMG has a little longer take down pins with a dimple in them; but other than that, I haven't seen any differences in any I have used. FCG's are different in that you can feel the difference in some of them. I can guess that AR15.com guys only like Colt and BCM parts and all others are crap and will fail within first box of ammo. Spend your money where you want; but LPK without FCG is not a place I would worry about.
I've seen LPKs sold by several different companies and I honestly couldn't tell a bit of difference from one to the next. I wouldn't be surprised if there's a factory somewhere pumping out LPKs all day long and just slapping different name brands on the packages.