Competition also has a re-designed bolt carrier and recoil spring assembly. Also changed the rear rubber bumper.
New charging handle, and added a tab to the rear piece of the recoil assembly that fits into a new groove on the lower that isn't present on the Gen 2s. Probably this was done because of the complaints of 1.) the charging handle latch breaking and 2.) the charging handle gouging the lower.
I also read somewhere Rob from In Lead We Trust, measure the gas port and the PCC was larger than the Gen 2 but still smaller than the Gen 1. Sorry can't find the blog where I read that.