I guess I prefer 750s (HPL750/115x) just because they've got that little extra if you need it. I don't typically find that I'm running too many lights at full, so the higher wattage gives a larger range to play with. However, I find that it depends on what the space already has. If I'd doing a show at a theatre that has an inventory of s-4's already, I would rarely rent over their inventory and ask for different wattage. The only exception I could think of would be if the space is limited on power (distribution or dimmers). I run into those crappy leppi packs that can only push 1.2k and in that situation it is dangerous to try 2-fering anything when you have the 750s. Also, many of the storefronts in Chicago have limited power distribution so they stock HPL575/115x's just to get more lights into the rig. It really just depends. And while were on the subject, I would like to criticize ETC for their misuse of the ANSI code HLP. They were a major contender in the HPL lamp being produced thus their seeming ownership of the idea of a source four. But then the wanted to change the wattage of these lamps, in which case they should have gotten a new ANSI code. There should never have been two different wattage lamps with the same ANSI code, that defeats the purpose of having a code you can tell someone and be assured you are getting the correct product. You can easily order a BTL and know that you are getting a Q500T6/CL/P JCS120V-500WBP28 or "Tubular/Medium Prefocus/500w/120v/127.0 mm MOL/55.5 mm LCL" lamp. If you ask for an HPL now, you need to be more specific. GO WITH THE STANDARDS PEOPLE, that way we can be sure we are ordering what we want. ...I'm just saying.