what is more recomended and efectiveness:revive grenades or health grenades?

Healing grenades only help if you're the only one among a squad of medics throwing revive grenades into a large fight. That's basically the only time the healing grenades existence is justified; being thrown among a bunch of dead friendlies while other medics throw revive grenades.

Good one .
For me I use only 4 revive nades on medic and it's free xp..

Seems to me that because HEALING in this game is functionally irrelevant since the average time to kill in close quarters is like, a second...

I use both, but mostly revive grenades. If medics are throwing revive grenades into slaughterhouses for xp, the revive grenade will be the best for that, but if a bunch of medics are doing it then the first thrower gets xp, everyone else gets nothing, so the healer will heal them and get xp.