U making a come back racing again? The LiFe packs are great for single cell racing. I've got them in all 3 of my cars. Can go a whole night with out recharging them. We figure you use about 30 MA a run. And there 280 MA. So your good for the night. They are great cause there light and small and come with switch and everything on them.
I have not used the Epic, so I can't comment there. I have two of the Thunder Power units and they are pretty awesome.
Very small, lightweight, and really simple to use. They also just put out a firmware update last week so they will charge to 4.22v/8.44v in competition mode. You can set 25 (I think it is) memory modes on so switching between charges for single cell, receiver pack, etc. is really quick and easy.
My only drawback to the TP units, is that it can get fairly warm and there is no cooling unit made into it. I haven't noticed a single problem with them overheating, but they do get hot to the touch when charging at 10amps.