What is the better addon for a healer.
I've tried all of the addons available for healers and personally I most recommend Grid2
combined with Clique (not to be confused with original Grid). You can do literally anything with Grid2. You can setup as many indicators as you wish, each indicator viable for any combination of buffs/debuffs that you desire (you can fill out your own custom debuffs/buffs for various boss fights & classes, etc). The sky is the limit, really, in terms of customization with Grid2.
The downside to Grid2 is that it's not so obvious when trying to set it up for the first time. It takes a little bit of time to get used to the way the options are laid out and how it works. I'd say it's probably the hardest one to setup out of any of them.
My next recommendation would have to be Vuhdo. It's the next best in terms of customization and features. Plus, Vuhdo does offer some features that Grid2 doesn't which, for some players (depending on your playstyle/preference) makes it more useful/handy to have.
Healbot isn't bad, it's definitely a usable healing addon, but I don't feel as though it can compete with the features & level of customization offered in Grid2 / Vuhdo. Healbot's more basic without some of the robust features that the other two have.