if I actually had a "regular style" piston seal that worked as well as a properly fitted oring seal I would be using it rather than messing with cutting and fitting an oring sealed piston cap. I'll give some personal opinions to your questions.............
"Do you like it because you can a tighter velocity spread?"
While the velocity spread of a properly fitted oring seal is pretty close, I've also had good aftermarket piston seals give VERY close velocity spreads.......the "fly in the ointment" for me has been that the "POI spread" can be "temperature dependent" which created havoc with early season FT matches where the temps can be "snow flurries" in the morning, yet mid 50s by the end of the match. Years ago both my brother experienced a 1" poi shift at only 20 yards during such a match where we did our zeroing in snow flurries and finished the match with temps in the mid 50s. It was at that time over a decade ago when I experimented with oring sealing in an attempt to minimize the contact of "rubber and lube" between the piston and receiver, thinking that changes in "rubber" durometer and lube viscosity was aggravating the poi consistency. Anywhoo......IMHO, form follows function, so while I personally would like to simply use a good piston seal, I've had a more consistent poi IF there is a large temperature shift due to ambient temps, sun heat load on the gun, etc. during a match.
"Or that its easier to get lower power?"
NO! Its actually HARDER to get lower power since "sliding friction" is less relative to a parachute seal. Matter of fact, for my HW77 I actually use a light wire after market spring to keep my velocity from exceeding about 900fps with CPLs. Normally I can count of at least a 50fps velocity boost from a properly fitted oring vs the parachute seal if I used the same spring. LOL.....at the beginning I used the factory spring in my R9 with the oring sealed cap and actually shot a bit with CPL velocities at 960fps. The R9 was much too jumpy at this velocity so I made efforts to minimize oring sealed velocities via aftermarket springs.
"Or that you have to work on the rifle more"
LOL....nope, it's been my experience that a well fitted oring seal will outlast a couple good aftermarket springs, so if you're replacing a spring you might as well also roll in a new 25 cent oring.
"seems that you guys that are posting are always tearing into your rifles every thousand shots or so"
LOL.....this happens regardless of the sealing method, however it not usually due to the oring going bad! Here are a couple pics of worn factory R9 parachute seals next to early oring sealed piston cap components......
Notice the "factory induced" slices on this R9 piston seal.
"Or is it a tinker kind of thing like how can we improve the wheel?"
Well.....I think that you may have nailed it here......"how we can improve the wheel". Hummm....perhaps it should be how we ATTEMPT to improve the wheel.