Hey I just hit 90 and I have been using disc and holy through out my leveling span in dungeons and like both. I just want to know which one is better for heroic 5 mans and then when I start LFRs.
Disc definitely for 5 mans just because of the dmg output and simplicity. 5 mans are rather dull to heal anyway so spamming smite will make you feel worth at least something in the group.
About LFR, I'd still go disc but if you don't feel like to spam the smite too much holy is a good choise also. Like holy there because mostly there isn't that much to heal but when the s**t hits the fan you can come in with a great burst and save the day!