Topaz Carbuncle vs Titan-Egi?

Carb = HP 2086, 70p single target, 70p AoE, 20% dmg reduction, 70p Stun
Titan = HP 2048, 85p single target, 70p AoE, 20% dmg reduction, 70p Stun

I don't see any difference but carb having little more HP while titan does little more dmg with ST move.

Can anyone please explain why I would play smn vs acn?

Thank you

Potency does not equal damage dealt. Topaz Caebuncle may have higher health, but may lack in other stats.

Garuda-Egi and Ifrit-Egi do a lot more damage than Carbuncle can, that's your role as SMN in parties. You typically don't want to be using Titan in parties so tanks can do their job properly, but there will, of course, be situations that may call for him. Not to mention SMN gives you access to the amazing Fester spell, and you will gain the ability to do Hellfire, Aerial Blast, or Earthen Fury. I believe SMN also gets a second pet strength buff.

Solo, you might want to stick with Arcanist for the added versatility and I believe the more balanced stats.

Well I'm acn / smn solo while in parties I switch to sch most the time. I'm just trying to see the benefit of having titan out compared to carb.