The Sniper can compensate for altitude, it has a map sensor and iat sensor both. I believe Fitech does too but I'm not sure. I was looking at both but the Sniper has more features so I went with it. I'm very happy with it, I have probably 1500 miles on it now. I did have some trouble when I added timing control but I believe it was caused by my wiring and how I routed it. I'm redoing that now and going to try it again.
If you decide on a Sniper I recommend purchasing through
www.efisystempro.com they offer their own Holley trained tech support and have been extremely helpful and easy to get ahold of.