Router - Belt or Ballscrews

There seems to be a good many off the shelf linear-actuators, the
majority of which are offered with either belt or ballscrews (some
leadscrew and some linear motors too) with a choice of bearings and
assembled on aluminium extrusions that can be bolted together to form
a gantry or moving table router.
Given the large price difference, the belt driven units seem pretty
good, but are they any good for a router ? I don't see commercial
routers using them, but the specs seem ok on paper.

Rab