I am thinking about getting a new colt lower with the trigger upgrade. Are these good or would it be better to get a lower and install the JP trigger? Thanks

It all depends on how much you want to spend.  The Colt unit is basically just a much smoother and lighter version of the stock trigger, but it is very cheap compared to anything else out there.  The JP is a much better trigger, but you do pay for the quality.

Unless you really want the Colt name on the side of the lower, you could get a Bushmaster or RRA lower with the JP trigger for about the same as a Colt lower with the trigger upgrade.