I'd go for a single cell torch with NiMh. Preferable two. One headlamp and one hand-held.
My most used AA-headlamp is a Zebralight H51Fw headlamp. It has been discontinued and replaced by H52Fw.
My latest purchased AA-torch was a NiteCore Sens AA.
I highly recommend both. But only with rechargeable NiMH or Li-Ion, not with alkaline.
My latest purchased torch was a Convoy C8. Also very nice, but strictly 18650 Li-Ion.
Single alkaline cells are not good for high output torches or headlamps. The chemistry means that a high discharge means a lot of the energy is lost. But for low output and long runtime torches and headlamps single alkaline cells are fine. Also if multiple cells are combined then the discharge is distributed between the cells and the alkaline batteries are able to give off much more energy.
For high output single cell torches rechargeable NiMh or Li-Ion are much better than alkalines. Especially since the high output means that the cells have to be changed often. For rechargeables that is no problem.
One problem with multicell use is that if there is one cell that isn't as good as the other, then that cell will reduce the total capacity of the battery pack. In some circumstances, like RC cars and flight, batteries are even measured and matched to ensure that all the batteries in a pack are as similar as possible. So single cell torches may be more efficient than mulitcell ones because of this.
Rechargeable NiMh and Li-Ion batteries can be used for low output torches as well. But some care should be taken. Some torches meant for alkalines may have *very* efficient step-up circuits that allow them to drain the very last joule from an alkaline battery. (Google "Joule Thief".) That is fine because that alkaline battery is then disposed. But for rechargeables a very deep discharge may reduce the life of the battery. Often Li-Ion batteries have a protection circuit to prevent too deep discharge that may harm the battery. Might even cause leakage in Li-Ion battieries.
NiMh used to be difficult to store charged. They lost a significant amount of capacity every day. But newer LSD (Low Self Discharge) NiMh batteries can be stored charged for months and even years with only a small loss of capacity. They also go under names like Ready To Use and Eneloop, depending on the brand.
Eneloop batteries by Sanyo (now Panasonic) are often considered to be the best. They are also pretty expensive. I have a bunch of them and am very happy with them. I also have a bunch of 3XAA to D adapters that allows me to use my rechargable batteries in things like radios and torches that takes D-cells. I can use 1, 2 or 3 AA Eneleoop cells instead of one D-cell.
IKEA has their own series of LSD NiMh, "LADDA" as AA and AAA. ("LADDA"="CHARGE") They are rated for fewer recharge cycles than Eneloop, but are otherwise about as good, or even better in some regards. They actually seem to be slightly *underrated* by IKEA. And they are much cheaper. When I need more NiMh, I'll get the IKEA LADDA instead of Eneloop.
So for persons that go through a lot of AA or AAA batteries a few sets of IKEA LADDA batteries and a good charger is hard to beat for cost. NiteCore i2 is a good NiMH-charger that also can charge Li-Ion-batteries.
A thread about IKEA LADDA on a flashlight forum:
http://budgetlightforum.com/node/26725
IKEA LADDA:
http://www.ikea.com/gb/en/catalog/products/00240585/
3xAA to D adapters:
http://www.ebay.com/itm/10-Parallel...ase-Box-Convert-3-AA-To-1-D-Size/291031940502