300 backpack hooked to 1500. I just fixed my 1500 and love it again. The nozzle selector, stream, trigger tactile feedback, etc. are all just so slick.
But since that involves work, just go with whatever you prefer. If your friends are of lower skill level, you can up the challenge for yourself and take a 150, Colossus, etc. (Believe it or not, I had to do this with a 270 against opponents who got more exercise than I did, but weren't quite able to take advantage of that.)