Biggest difference is the skill level of the operators. I was selling an old truck mount years ago and as a demo, we tried it out on one of the buyers customers carpets. I presprayed the place and gave the buyer the wand. After a while I took it over to give home some pointers. Same wand, same prespray, same carpet, my area was noticeably cleaner than his. Over the years you develop an eye for soil and how it's releasing. Some people would look at that floor and say it's clean. You look at it and you can see the dirt. More power always helps of course