All helmets fit differently depending on your head. So the priority should be to find one that feels good.

Now, at equal comfort, I have had two Bell helmets. The main difference is vents (hence head temperature) and weight. I found weight to make a big big difference, especially for long rides (2+ hours). A lighter helmet caused less neck pain. The fact that my head remains cool (in 15 deg Celcius + temperatures) also means that I get less tired, especially when climbing.

I also have a Giro Atmos helmet, their top-of-the-line thing. Very light, but I really dislike the adjustment mechanism. And it just doesn't fit my head right. It's now on my dear partner's head, and it fits him well. My Bell Sweep-R is half the retail price of the Atmos and fits me much better without being that much heavier. And the closure system works better.