I can't speak for the original poster but IME, NiMH rechargeables are not reliable...especially once they are used for awhile. I do consider myself to have good "battery hygeine" so to speak. I take care of them properly. So I am forced to either wing it and hope the NiMH batteries don't die (but they will eventually) or go the external route...which I am currently in the process of doing with a LIon.
Also, I'd be curious to know how much time you get with the 2700mAh @ 24/96?
Never tried 24/96, maybe I'll run a test tonight.
But in terms of battery types, I've read/heard that NiMH are more reliable than Lithium ion types, and unlike Lithium batteries, they do not continually lose capacity every year. I think the main choice here is NiMH versus alkalines, which will be the most rock solid. Lithium AAs will probably give you the best battery life and reliability. Been using NiMH for my R-09HR (and R-09 previously) for over a year and never had a battery fail on me. I'm sure it'll happen eventually though.