You may be quite surprised at what your trainer can actually do if you tune it up.  Start with increasing the throws of all the surfaces.  Then move the CG back a little at a time and do something called dive testing (search for it in the glider forum as it's been described how to do many times) until it's fairly far back.  Finally learn to add some rudder to go with the aileron inputs.  Using some rudder with the aileron really snaps the roll rate up a bunch.    With the setup indicated the model will do rolls, immelmans, stall turns, likely fly inverted but if it's got a flat bottom wing it may not like doing outside loops.

As for the original question much of the added ease for flying the bigger version comes from the higher weight of the big model and it's inertia that damps the movement compared to the more instantanious response of a shorter moment and lighter weight on a smaller model.  I believe the term is "swing moment"  You can feel this yourself.  Flick a pencil back and forth like a windshield wiper and it's easy to do it fast.  Now try the same thing with a 2 foot length of 3/4 inch dowel and you'll find you can't do it as fast.