I'd get normal eneloops, for the price of Sanyo XX you can get more of the normal eneloops. My memory has it that the normal eneloops retain higher voltage under high load too.
Sanyo XX aren't really "gen 2 eneloops", they're rather a hybrid between the regular high capacity Sanyo 2700 technology, and the low-self-discharge eneloop technology. The normal eneloop provides excellent power capability, retaining higher voltages under load, and excellent self-discharge properties, allowing you to store fully charged ones for 5 years or more before they lose their charge. The sanyo 2700 has higher energy (energy is not same as power), sacrifices power and has higher self-discharge. You wont get the benefiit of the extra 700-800mAh unless you use them right after charging. XX sits in between.
To take a car analogy, the eneloop is a V12 engine with a smaller fuel tank. The Sanyo 2700 is a 4 cylinder 1.4 litre engine with a large fuel tank. However, the sanyo 2700 has a large hole in the fuel tank so it leaks. Sanyo XX is a compromise between the two.
This applies equally to other brands too, I'm just using Sanyo as example because it's the best on all fronts.
Now as for voltages, in a high performance regulated flashlight the alkaline might provide higher voltage for the first few minutes, but after that the nimh battery will be providing higher voltage. Whether that actually gives higher brightness or not depends on the circuitry. In a regulated light you'll probably find that the brightness stays fairly constant with voltages (under load) down to 1V or so. I would expect the nimh battery to maintain higher than 1V for longer than the alkaline battery. With the alkaline battery you'd get a longer "tail" of less than full brightness, the tail might be so long you don't actually notice the gradual decrease in brightness. With nimh the tail would be shorter. Some other regulation circuitry, on the other hand, will switch the the next lower brightness level if the battery is not able to provide enough power for the requested brightness, causing a noticeable step-down in brightness, making it easier to notice when the battery is getting low.
To return to our car analogy, the alkaline battery is a weak but high-rpm 2-stroke engine with a large fuel tank. For some things you might want and need 20,000 rpm, but if you put any higher load on it the engine it chokes and sags to lower rpms than the nimh engines.
Energizer lithiums on the other hand have excellent voltage under load, and high capacity. On top of that they have fantastic shelf life. The perfect battery to stock up on for apocalypse survival.
In summary, I'd recommend the regulat eneloop batteries.
