Got to go to bed but I'll answer this at least.
If the party doesn't end up getting wrecked, then Healer B was more useful.
If the party gets wrecked, then Healer A was more useful.
I'm not suggesting that it's all or nothing either, by the way. As I have said repeatedly, if the healer feels that a disaster is unlikely (not just in the scope of the entire fight, but within smaller portions of the fight as well), then they can make the call to use cooldowns offensively. All I'm saying is that if the healer makes that call and they ended up being caught without those cooldowns up when they were needed, then it's the healer's fault for taking that risk.
I am generally Healer B. I just play in situations in which I would be an idiot to try to contribute to DPS regularly with my cooldowns because, more often than not, I need all of my cooldowns just to prevent a wipe. If I'm playing in farming parties, that changes. I start to take those risks because the chances of a disaster occurring is low at worst, and negligible at best.