I find that the overlay gives me much more flexibility - particularly as you can resize the pattern. You can get a few extra options with the edit / fill by pressing Ctl-Shift-F immediately after laying down the pattern (allows for changing opacity and blend mode).

The edit / fill commits the action and you can only go back and change it much further down the line if you have saved history, whereas the layer style you can change at any time.

I'm sure there must be good reasons to use the edit/fill for patterns in terms of putting stuff on the same layer and blending it in with the pattern, but off hand I can't see how they would help with the way I map, but that's just me.