I definately like the bat effect better. However, both animations seem to be a little slow. (That may just be the gif though.) Also, in both animations, Alucard seems to be in a strange pose. I feel like the animation would pop more if alucard were to fling out his cape, which would then become the bat's wings. If you end up going with the smoke animation, you should probably brighten up the colors and add a little "flash" to them.
About your alucard sprite in general, I wanted to point out some little things that kind of throw me off.
- Alucard's face appears a little green, and I don't see the colors many other places in the sprite. His face pops out, but in a way that makes it seem like it doesn't belong in the sprite.
- Alucard's face never changes its position. A lot of his movement appears unatural due to this. This also applies to his hair.
- Your lightsource is inconsistent. Light seems to be pointing up at his face, downwards on his cape, and from the side on his body.
- In the fireball animation, Alucard's cape stays suspended in the air for quite a few frames. You should probably make the cape fall down after he puts his arm up to make the animation look more natural.