A couple of things to consider when picking head lamps is: (1) how much weight do you want to carry on your head? Headlamps that run on 18650's are generally going to bigger than lamps that use AA or AAA batteries (and often rechargeable models). There's a reason why 18650 head lamps generally have the third strap that goes over the head. The bigger, heavier lamps require it for stability. Some large lamps even have the battery pack on the back which isn't very good when you're lying on the ground working on something overhead. (2) Colour temperature. I generally prefer warm whites for camping and night hikes but for working on my car, I prefer neutral white or even cooler. Generally, I find that if the application requires brighter light then I opt for a cooler colour temperature. For low light level applications, like chores in a tent before turning in for the night, I prefer a warmer light. (3) If you want to use this for things like camping, what mode does the lamp start up in? If your eyes are already dark adapted, you don't want a headlamp that always starts up in "high" or even "medium". Again, if you're using this for camping, does the head lamp have a decent moonlight or firefly mode (< 1lux).
FWIW, I have warm-white Armytek Tiara, a neutral-white Fenix HL50, and a neutral-white Fenix HL23. They are all AA lamps. For working on my car, I gravitate towards the Fenix HL50.
In my collection I also have an 18650 based hand flashlight because everyone should have at least one >1000 lumen flashlight. (I find the best combination for night hikes is to use both a head lamp and a regular hand held flashlight.)
The only light I'm a bit disappointed with is the HL23. Build quality is excellent but it tends to throttle down its high mode too quickly. My HL50 doesn't do that, and as a bonus, can use CR123 batteries if you ever need a light in extreme cold weather where alkaline, NiMH, and even regular 18650 type batteries aren't happy. Only downside to many Fenix models is a lack of a good moonlight or firefly mode.