In TSD, we used to wear the bare minimum (head gear .... sometimes, shin and arm guards or gloves ... cups for the gens). But it was light contact. We sometimes only had boxing goves on. That's it (for tournies, we needed the shin and arm guards, head gear, and cup).
In TKD, we do the whole thing (chest guard, head gear, mouth guard, shin and arm guards, and cups for the gens). It's light contact for beginners, and hard contact for red and up. The advanced students usually go pretty hard, and I like the gear (at least the head gear) so I don't get hurt. But I do my fair share of trading hits also. But, the chest gear, I hate. Just for the fact it is limitating for my kicks (as in, I can't kick as high with it on, because it restricts my kicks). But when I'm up against "bubba" who kicks hard, it's nice to have it on.
But having done both hard and light contact, most of my sparring injuries came from light contact (lack of gear and lack of control of my sparring partner).