Seems to me that there are significant pros and cons:
PMAG: Install is simple like a mag, but you have to remove and inspect every 100 hours as their is the possibility of it failing in such a way that it will drop metal into your engine (like a real mag). Some report the timing being too aggressive and high CHTs, others report no issues, others report they backed it off with an EICommander, others report they set less base timing. Another con is electronics bolted to a hot vibrating thing.
SDS CPI2: Install is much more involved with coils, wires that pass through the cockpit, magnet holes on the flywheel, etc. Once it's flying you don't need to do anything beyond inspect the wiring at annual. This system maintains it's own backup battery which eliminates all of the complexity of redundant electrical systems, but you have to find a spot for it and it's another battery to maintain. One nice thing is the ability to set whatever timing curve you want from the cockpit but you have to find a spot for the little head unit.
Others: Install is like the CPI in that you have a brain box and coils and pickup, but you need to design an electrical system able to provide backup power and/or detect alternator failure and shed load. Some have more timing flexibility than others.
From my perspective the power redundancy is moot given the CPI2's ability to maintain, charge, and swing to it's own battery backup. The real question for me is which is more reliable, which is more difficult to install, which is more flexible, and which will require more maintenance.
I'm much more comfortable with a battery backup than bearings I have to look at every 100 hours, and I don't care how hard it is to install it as long as I only have to do it once. 100 inspections are a deal breaker for me as I frequently do long cross country trips (I've been as far west as Platinum AK and as far east as OSH) so I would likely find myself in a situation where I need to pull the mag before a major trip, and knowing my luck, I'd find a loose bearing.
Others are much more comfortable with simple install and gears/bearings. I think the right solution is a simple matter of if you prefer gears, bearings, and generators to keep the fan going, or are you more in the camp of magnets, sensors, and backup batteries?
schu