"The new plastic aircraft" tend to be quite expensive to buy I think, certainly more so than the 1960's to 1980's airframes that most flying training organisations use. I wonder whether the fibreglass and carbon fibre airframes now being designed, will last as well as aluminium airframes have?
If by plastic aircraft you mean Diamond Katanas, they are pleasant (easy?) to fly, they are spinnable, and they have excellent performance (e.g. climb rate on hot days). Students seem to like them, and they have a good useful load. But they are expensive to repair, and are more prone to tail-strikes on landing than other makes - they do need to be flown, as opposed to stalled, onto the runway.
I liked the Robin 2160 quite a lot, but like all French aircraft anyone over 180 cm in height will be resting against the canopy...
On the plus side one does need to use the footrests to fly accurately, which is good for a basic trainer.