Make sure there is a good selection provided with the helmet so you can add them to achieve a good fit. Styles incorporate safety and appeal. Thinshell helmets have a thin coat overlying the foam liner. Foam only helmets are made up of a foam liner and are worn with a lycra cover. If these helmets have Snell, ANSI, ASTM or CPSC safety ratings, then all provide good protection.
Helmets come in many styles and colors.
If the size and shape are good, and it passes safety standards, choose the one you like best. Comparing price to value. Helmet prices vary greatly. A more expensive helmet does not necessarily equal a better helmet. Correct size and shape, and passage of safety standards are the most important features.