I really recommend gauntlets. They offer more protection, and they offer the added benefit of insect/wind/etc.-proofing the would-be gap between your glove and sleeve. And they just look cool.
Boots, as other people have said, rely mainly on fit to your particular foot. Other things to look for include height (at least up to your mid-shin), ankle protection, heel protection, shin protection, and resistance to torsion (you don’t want your foot to end up pointing behind you after a crash).