None are much.
You are talking only a few HP here and there on the gas engines and no all the totals do not add up and often the learn feature can negate the gain unless the programmer opens it up for the other items.
I went with a Diablo InTune handheld tuner, but not because I wanted to gain a ton of horsepower. My 2016 Z71 had some "issues" from the factory. The transmission program was garbage, the worst behaving shift behavior I have ever experienced. Also, the accelerator really needed to be buried to make the truck move the way it should.
The Diablo made it possible for me to adjust the transmission's shitty shifting behavior and adjust the throttle "boost" so that the vehicle moves without applying too much pressure to the accelerator. The throttle issue was just personal preference, but the transmission program is really a necessity in my opinion. The Diablo is a handheld tuner that can be used on many vehicles, so I can keep it even if I ever sell the truck. Plus, there's a guy named Lew who can modify parameters beyond what the handheld can do, so there's always that route too if you want to get more extreme with it. If you already have the tuner you don't pay as much for his programs. He goes by DiabLew on Diablo's forums.
The info below doesn't answer your question, but I figured I'd share anyway....
From the factory, my transmission would literally keep me locked into 3rd or 4th gear while I was making turns. Waaaay too high a gear for accelerating from 5-10mph. That made the truck bog down coming out of turns, unless I mashed the throttle. I understand the rationale for wanting to keep us locked into a higher gear (less revs, better MPG) but the implementation was done very poorly. Instead of dropping the vehicle into 2nd gear so the vehicle could get back up to speed, my Colorado would still have me locked into a much higher gear so I had very little power to accelerate after the turn was completed. So, obviously I would have to really hit the throttle to actually speed up at a decent rate. Well, doing that would finally drop it down into 2nd gear, but AFTER the truck would be at 3-4K rpm for a few seconds, which negated any fuel savings. Anyway, stupid engineering on GM's part, and I really hope they eventually fixed it. My dealer couldn't help me since nothing was "wrong". There have been hundreds of posts about that issue, but I did the program and it helped it a lot. Sorry this was so long, but more info is always better right? lol