Brand new forum member, 40 yrs in aviation both EAA, EAB and Commercial, CFI, ATP, EAA member since 1987 and built 2 kit planes.
Yes true a misfiring (traditional) magneto can cause loss of power and negate the 2nd mag, even if the 2nd Mag is functioning properly. THAT IS WHY when you learned to fly loss of power you checked the MAGS by turning one of the mags off and on, one at a time. Same with EMAG or PMAG.... Most of the problem post on EMAGS / PMAGS are from 2008 when they were new. They did have some past issues, which are history and sorted out. There is no ignition totally reliable.
The advantage of the EMAG or any EI is then advanced timing verses fixed timing. Yes the spark is HOTTER for EI but traditional Magnetos are no slouch. The other advantage is using Automotive plugs (cheaper) that can be gapped to a larger size making for a "bigger" spark. That advantage only really helps when operating well under 75%, think high altitude. All EI's hold a fixed timing say at that magic 25BTDC. Too much advance at higher power settings (above 75%) you can cause detonation and severe engine damage. Bottom line EI promises (and mostly delivers) easier starting and better efficiency from 2% to 4% may be more.
I just bought a set of used PMAGS for my current project so I researched it. I see some limitations still exist even with past issues sorted out. The big one is continuous maintenance. You have to remove the EMAG (this includes PMAG) every 100 hrs condition inspection. I think this is part of the magnet issue. Although fixed it is like any service bulliten on airplanes and engines, even if there is a limited problem and mostly addressed the SB stays for continuous airworthiness.
(Note EMAG does not make EMAGS anymore, they are all PMAGS (the ones that can be self powered). They do support EMAGS. I am not sure but they can likely upgrade an EMAG to a PMAG, but not sure.
The other limitation is the cooling. This is an induction coil ignition. Then coil is in the electronic ignition housing with the "distributor cap". Coils get hot spitting out 10's of thousands of volts 1000's of times a minute. So PMAGS require air blast cooling tubes. With canard pushers down draft cooling I think is better as long as you route cool are into accessory area, but in tractor engines that upper accessory case area where the mags are is kind of stagnant air wise, and heat rises and soaks the magneto area when you shut down on ramp. Not sure what max Temp PMAG allows, but they now have 200F / 93C tell-tale heat sensitive sticker on housing. Experimental, it is up to you to keep them cool and flight test iwith temp probes.
Note there is no distributor cap rotor in the PMAG like old car ignitions or aircraft magnetos. It is all electronic with a LOST SPARK. Meaning each cylinder gets 2 sparks per 4 cycles, one near top of compression stroke to make power, and one at top of exhaust stroke that does nothing, thus wasted spark. So it is "solid state" but there is moving parts. The reason for this is to save weight and complexity two cylinders are fired as pair together.
Other electronic ignitions require redundant electrical, ships power or no ignition. They also don't use the engines accessories case to drive a "MAGNETO" type accessory. Almost all other EI's use a fixed crank trigger off the engine case, and a magnet in the ring gear (technically not a flywheel but called flywheel by some). NO moving parts except the magnet in the ring gear. So except for the alternator belt breaking and taking out your wires or hall effect sensor it is very reliable. However there are wires all over and more external connections, plus the need for electrical power.
