Price
The final factor not mentioned. Once you add up all the probes and sensors the GRT EIS4000 will be cheaper. Believe it or not Spruce Aircraft has the cheapest price I heard on the basic EIS package, ($900 for the basic system), however if you want service with your purchase I know Stein air sells them and can help you more with questions. Bang for the buck the EIS4000 is the least expensive system approx $1,700-1,800 with Fuel flow, Cap fuel level and every probe you can think of.
BTW I just saw another new engine monitor in the EAA magazine, which now makes 10 or more Electronic engine monitors you can buy (some cost $4000-$5000):
Grand Rapids,
Rocky Mountain,
Adv flight Sys AF-2500,
Vision Micro system VM-1000,
JPI (who just bought out Vision Micro system),
I-K Technologies AIM-3000,
Electronics International Inc,
Dynon,
PCflightSystems EMON (for a pocketPC),
Insight GEM (CHT/EGT only)
Xerion Avionix EGView (new?)
There are a few more I don't recall. I think with the fact Micro System and Adv flight system have been sold, I guess you want something you know might be around a while. Both GRT and Rockymountain have been around for a while.
Cheers George