Hmmm..
We're sorry to have possibly offended Mary!
Let's say that power planes are like apples, and gliders are like oranges. We all have heard that both apples, and oranges are just great, and perhaps we've had the chance to try both... But,
If the objective is to eat apples, eating oranges won't quite do it. Sure, oranges are great, and satisfying, but they're still not apples!
If you have an objective to eat apples, eat apples. If you have an objective to broaden your horizons, then certainly eat oranges too, or instead. If you can afford to eat oranges more than apples, this is no longer a discussion about pilot training (sorry, fruit eating), but budgeting.
If both the power plane, and the glider, were sitting on the ramp side by side, none of us would be recommending to the Mighty, that he/she accept the flight school swapping back and forth between these aircraft types, as was reported about the swapping of instructors.
At this stage, consistancy!