This is just my opinion, but I played both a Sorc and Trooper (BH mirror) during beta and am playing a Sorc now at launch.
I feel like a Sorc makes for a better healer because of easier resource management (for a Trooper your Ammo would regen slower if you had less of it, I assume BH is the same way with Heat), no cooldown on your quicker heal, and a damage shield that the Trooper was lacking. On the other hand, the Trooper seemed to do better damage than the Sorc, especially when it comes to AoE. Additionally a damage-specced Trooper gets a hard-hitting attack with an armor debuff, and an armor piercing self-buff.
It really depends on what you prefer, but I decided that the Sorc was a better choice for me as a healer.