I have flown several with the P-100 and they do feel lighter, although I don't find an issue even with the heaviest UF I have flown. The energy retention is better with the heavier set ups. Flight times are probably longest with the P-160 turbines! You are on full gas for much less time (unless you are a nutter ;-), The smaller turbine you tend to be on full power more when the turbine is at its least efficient. I've watched Jame fly his and he has the throttle use of a helicopter pilot (means he can use the throttle stick actively) and uses the momentum to the maximum, for long flights.
I'm going to build another UF for myself soon and update the set up with a P-140Rxi which to me is the ideal set up.
Throttle response is not as critical as people think! Its all noise (giving some false relief) the draggy airframe still has to accelerate, probably not much faster than the old turbines spool up at...