There is a third option - convert to studs & nuts!
I guess it depends upon how often you change your wheels. I think spacer and longer bolts is the least favourable as when you offer up the wheel to the hub, the spacer can move independently to the wheel and the hub, so you can have a bit of fun lining everything up. That's why the front brake discs have that little screw in them, to stop them rotating.
The bolt to hub or conversion to studs - not much in it I guess. You'd need to price them up. I know the bolt to hub ones also potentially allow you to change stud pattern to fit other wheels.
I have studs & nuts front and rear - that's mainly because it makes changing wheels at track days an awful lot easier, but they also carry my spacers on the rear. Badger Bill can get the necessary bits and bobs.