As said above, clubs generally prefer active glider pilots with not much power experience rather than the other way round.
This is because a) they have an appreciation of what happens on the other end of the rope and b) having a soaring pilot in the tug who can read the sky and optimise the tow in terms of lift (on tow) and sink (descending to land) can save the club a *lot* of money in fuel. Also, reducing the turnaround time keeps the aerotow queue happy and may generate extra launches that there wouldn't have been time for otherwise.
Having someone who has spent the majority of their flying time doing fully held off landings from relatively tight circuits, while keeping a good lookout, makes the training much easier as well.