1. I play both BC and FS, but FS more because it is more useful.
2. Being a tank that can die (I'm looking at you, knights), being able to bully (both with BC and with buffs/heals/puri)
3. FS: Important role, good amount of tankiness and squishiness that you can alter with build choice, has some skill build variety
BC: Strong attack in both PvP and PvM, tanky
4. FS: Boring to play and takes very little skill, only a tiny bit of "common sense" (i.e. don't go around tossing the biggest heals as soon as the CD finishes on the next person you can heal when he is at 95%hp). Too easy to be "useful" by just spamming skills/flames. Self MSPD buff is way too small, even when putting on a couple of ms pieces that decrease tankiness, so it isn't even just "hard" to heal people far away due to being bad at moving around; it is only "hard" because you can't reach anyone in time. "Mid, don't go too far from cleric!"
BC: Also pretty boring to play because you spam: target enemy, attack enemy, voltage storm, and voltage jolt. Also spam AOE Puri. There is the occasional skill of muting one cleric/person and stunning the other cleric/person, and maybe Purifying a Cold Snapped person that can't run away, but not really. You just do melee attacks and let it rip. And nobody hits you because you are tanky, so they rather just kill the easy squishies over and over again, or attempt to and get lots of dmg inflict.
Both do not have enough skill choice. I want an FS to be able to focus on more HoT heals, or more Instant heals, or a hybrid of the two. Maybe an FS that summons "heal-type summons" that you can set focus on one player, with different summons healing different amounts either instantly or HoT-like. These would be monsters/summons that follow a player around, not like possible healing gadgets or whatever that the Artis might get. An FS that relies more on chance of CCs or something else instead of either being: tanky or not tanky and rely on self-heals. FS currently only has three build choices: tanky with book and no flames; not so tanky with book and flames; shield with flames and maybe aoe sleep or aoe stun or mana shield or whatever else a cleric could want.
BC you literally sit around doing nothing. It's like how the Katars were before their recent aspd/accu+cleric aspd nerf. Sure, the aspd buff nerf also hurt BCs, but not very much. Can't get enough ASPD to kill someone before they run away? Spam stun them.