All depends on the ohms you want to end up with. With a micro coil, since most of the coils are touching, it takes more wraps to get the same ohms, than if the wrap was spaced.
For instance, a 28 Kanthal spaced 7 wrap around doubled up 3mm silica, will give you around a 1.5 ohm coil. For around the same ohms, it takes about a 10 wrap micro coil. Now this all subjective. It depends on how tight the coils are around the silica, and the final length of the wire. The micro coils have a tendency to be a little more uniform since most people use something round, like a drill, to wrap the coils around.