I would say that you couldn't go wrong with either. RF is making some pretty solid stuff now. Just look for which one is cheaper and see if either of them is missing any kind of feature you would want.
thats a hard one, I havent heard that orion amp but I had that RF amp. It was ok I wanted more from it If i had a choice I would go with orion because it is at 13.8 volts i think? The Rf was at 14.4. and you wont get what it says you will unless you get lucky and get 1 of the amps that push 2400 watts on the birthsheet