I use the KX2’s internal battery, limiting me to 10w. That’s a 3db increase, but one that is overcome with better or higher antennas. I don’t think it’s just the output though. I think it’s that combined with the built-in adjustable speech compressor, the RX and TX equalizers, and a few other features. Early last Fall, I re-worked a summit that took 3 attempts to finally successfully activate with my 817 earlier in the year. The successful activation took me 2hrs to get my 4 contacts, one of which was on 2m FM. I went back after getting the KX2 and knocked out 5 in 30 minutes, including set up, fixing some hot tea, and generally jaw-jacking with my buddy who was making his attempt with the 818 he recently purchased. It was like night and day both between my own activations there and between mine and my buddy’s on the same day.
Chris