R.J.
Huge vote here for NOT a bike helmet.
Skate Helmet.
Why?
1) Bike helmets are designed to protect from forward directional force injuries. AKA for adults, moving forward at a high rate of speed, going over their handlebars. NOT for side impact, nor rear. They have limited coverage, and the sudden sharp edges of bike helmets in a non fwd directional force injury usually "catch", and cause severe cervical spine damage. GREAT for adults going over handle bars. LOUSY for kids going forward, sideways, backwards, etc. Especially at low speeds (still with enough impact to create traumatic brain injury, but the slow speed changes the impact absorption), and more traglically, it's slow speeds where the sharp edges often catch, and create cspine injury where none would have existed even bare headed.
2) Skate helmets have roughly twice the surface area of bike helmets. The protect frontal, temporal, and occipital skull. They are designed for multidirectional impact at high and low speeds. They are rounded in order to move the cervical spine in a fluid motion (if at all, the shape often deflect blows completely) to prevent damage to the cspine/cns, disarticulation/internal decap, and soft tissue damage.
Added NON-health benefits to skate helmets :)
- They look cool, so kids are more likely to wear them.
- They have different thicknesses of interior pads, so the same helmet can be worn longer (thicker pads changed out for thinner pads) with no loss of protection... so you save money in the long run. Skate helmets are more expensive... but they're just worth it.
- They're multi-sport: Skating, Rollerskating, Razoring, Biking, Skiing, Snowboarding, climbing, horseback riding, kayaking. Again, it's a money saving thing.