Well, a parallel gives more surface area. Its easier to make than a twisted, because you don't need a drill. But two standard coils right next to each other is going to be a lower resistance than a parallel (because the winds for each wire in a parallel are further apart... there is a second wire in-between them). It really is just an additional way to hit a resistance target.
But, at least on a mech (this is all I use), any kind of well wrapped microcoil at low-resistance will give great flavor and vapor production. If you are using one of those high-power regulated boxes, the type of coil matters even less. You can just wrap any kind of coil you feel like and then keep pumping the watts up until you get the flavor and vapor production that you like.