Hi Jeff,
Not sure about the difference in water lift, but woodbridge do a replacement vac for the excel at a much better price, we've used them a few times and they seem to last longer than the ones from extracta
They look almost identical, I would say they probably just a bit noisier but not much.
I think the 7.2 have bigger fans in, so probably cool them down more if using them a lot.
regards
steve