Having flown a Bulldog, Grob and T67A and T67M, I can say that the T67M is streets ahead of the others. Yes it has a slow roll rate, but it has the performance for higher energy maneuvering and station keeping in formation at high AoB.
The T67M had a very comprehensive avionics suite making it a great trainer.
As for 'frame longevity, I'd wager our plastic friends will long outlast the Aloominum ones.
I believe Slingsby went bust after the grob deal. Great shame.