> What i find interesting is that petzl probably sells more tikkas alone, and likely even more of a single model say the tikka 2 ... Than all sparks, zebras, etc combined
Well...yeah...Petzl is mass market, so they sell a ton of mass-market 3AAA lights. Zebra and Spark are not mass market, don't have anywhere near the distribution channels, manufacturing capacity, or marketing muscle. They are boutique / niche products, emphasizing build, tint, lumens, burn time, etc.
The reason 3AAA is the typical mass market headlamp, is that 3 x 1.5v cells gives enough voltage to fire an LED without any additional electronics to increase the voltage. It costs more to make an LED that burns on two or one 1.5v cell; these require boost circuits. Downside is, AAAs are relatively inefficient for their size, which is why many flashlight enthusiasts shun 3xAAA lights in favor of 1xAA lights.
Petzls can generally be purchased for less, and purchased in brick and mortar stores. Inexpensive, widely available, and durable...that's why Petzl has such a strong following. If you love Petzl, go for it. I'll not try to change your mind.
Regards the title of the thread:
...there is no such thing. There are only headlamps that match your needs to greater or lesser degre. If your need is to buy it from REI, well there are good headlamps that fit that need. If you need ultralightweight and don't care if it takes exotic batteries, a different one. Maybe you need to spend a lot of money so you can brag about how much you spent. Or the opposite, maybe you need to spend $30 or less. Want excellent tint? A different one yet. Me, I need a waterproof, single cell, high CRI light that can double as a handheld and has a floody beam. You may not need or even want those things.
No such thing as a "best headlamp."
There is only "best fit for your personal requirements."