Unsure which Healing Spec to choose.

[Töasty]

Holy is fun in BGs. Nothing like hitting power world shield and sprinting away. Cure disease removing poisons on yourself is nice too. Having HW:Sanctuary, lightwell, PoM, CoH, desperate prayer, and stronger renew gives you a lot of spells you can cast/use on the move. Blessed Resilience, guardian spirit are really nice, combined with desperate prayer. Holy Word Chastise is really nice too. Glyphed CoH healing 6 BG players instantly is nice.

Reflective shield is fun in BGs though, watching someone do damage to themselves is always a bonus. Inner focus with strength of soul talent is really nice too. The only "problem" with disc is that they nerfed the duration of pw:s so preshielding a bunch of people in a BG will not only burn your mana but will more than likely be wasted unless they are actively in combat.

Either spec is fun, and both disc and holy you can make one spec that can heal pvp and 5 mans just fine.

[Fulltimejoke]

Disc all the way... you may notice a dip in aoe healing performance, but it's not gonna be gamebreaking... as long as you use your prayer of mending / prayer of healing effectively and fill in the gaps with direct healing spells (or renew even). I tried to go Holy myself for a bit in 5 man's and it was just bad compared to disc, I felt like I had to drink after every other set of mobs. Was I doing it wrong? Possibly/probably... but I could do the same amount of healing with less mana as disc, so the decision was easy for me = Prevent damage > Heal damage.

The one time I tried Holy in a raid, my guildmates were clicking the lightwell before the fight (amazed to see one? /shrug) and wasting charges, and that pretty much sealed my fate with Holy - never again lol.

[Ynna]

Disc all the way... you may notice a dip in aoe healing performance, but it's not gonna be gamebreaking... as long as you use your prayer of mending / prayer of healing effectively and fill in the gaps with direct healing spells (or renew even). I tried to go Holy myself for a bit in 5 man's and it was just bad compared to disc, I felt like I had to drink after every other set of mobs. Was I doing it wrong? Possibly/probably... but I could do the same amount of healing with less mana as disc, so the decision was easy for me = Prevent damage > Heal damage.

Your personal experiences don't mean one spec is superior to the other. You yourself pointed out your inexperience with Holy and manamanagement is rather different for both specs, so you going out of mana can probably be attributed to that and not to any problem with the spec. One last thing, and this is something of a pet peeve of mine, preventing damage is only better than healing damage if the damage would be lethal otherwise. No (unavoidable) incoming damage is designed to be lethal, so a Shield acts pretty much like a front-loaded HoT.

And I don't mean to attack you personally. I just want the OP to make an informed decision and while anecdotal evidence is valuable in that, it needs to be nuanced.