Good call. I've been testing AAs for nearly 20 years now (sad I know) using a routine that hasn't altered over that time, for consistency. Though it's no longer a 'real world' test as it was when I started out - the real world having moved on a bit!
But whatever way I measured it, the black Eneloops were more than 10% better than the best of the rest - and for some applications more like 20% better.
This rather fuzzy pdf is a reprint of my report in Arrivee a couple of years ago.
A caveat is that whenever you buy a 4-pack of cells, you are taking a gamble - especially for things that use 4 cells at once like front lights - because any set of cells is only as good as the weakest one. For a 4-cell light (given how critical this can be, ie does it get you home or doesn't it) you really need to buy an 8-pack and find the best 4. For 2-cell devices like GPS, it's great if you are able to identify the best 2 out of the 4-pack, and mark them as a pair.
Energizer Lithiums can be 'better' in some specific areas:
* being half the weight - for ultimate runtime per weight carried, 4x Lithiums are usually better than 2x Eneloops - though even then it depends on the device - it's true for Garmins for example, but it wouldn't be true for Hope front lights.
* in applications where a very low voltage is still usable - such as bicycle rear lights - then primary cells and especially Lithiums, make a lot of sense - they'll carry on running long after a NiMH will have fallen off the cliff.
* for backup purposes - because their shelf life is very long. For example, on long trips I cycle with a backup GPS stored in my bag - this has lithiums fitted, for light weight and long life - it's had the same pair in for about 4 years now.
