I'd be interested to know what exactly the Haltech can do over UpRev that got you the 20HP. I'm gussing rather than Haltech vs UpRev, it was just a better tune you got and a different dyno. Dyno's can easily read +/-10HP for no good reason on different days, so could be just a better tune and different dyno coming into effect.
From what I've heard on the interweb, UpRev is good, but has its limits. I have read that once you get into proper FI and NA builds it can be more performant to use a stand alone unit but these have their problems too, so its mostly down to the tuner. UpRev is the best for the window it operates in, but I get the feeling you can only push its parameters so far past the stock ones before it wont give any more, whereas stand alone will just let you keep cranking away.