Regeneration also pulls critters out of combat, but taps them (might not be worth loss as a future blocker)
A probably unneccesary clarification: Only if the creature dies and the regeneration is actually used. Setting up a regeneration shield alone will not tap it.
oh yeah, good catch. For the purposes of triggering attack special abilities like on Sun Titan, or the eldrazi annihilator ability, regen can still save your creature if the block goes badly if you attack to simply trigger that ability.