As with most things in cycling, it depends. They all protect your head fairly equally, so the differences are in fit, weight, ventilation, aerodynamics, and looks. And of those factors, some are more important to some riders than others. Find one that works for your priorities and don't be afraid to spend the money. On the other hand, there's no need to waste money on a needlessly expensive helmet. For example, I loved the Specialized S-Works helmet from a few years ago, which was the top of the line then, but found out that the current S3 is essentially the same helmet at a much lower price.