I agree, the Firefly is a great machine, but it drinks fuel and is a bit noisy - great fun, just don't have the bad habit of picking up the wing with rudder in the stall.
The PA38 is a sweetie but can be unforgiving - the PA28 has blind spots when teaching nav.
The Bulldog is strange for students to fly left handed, but lovely to play with.
I think, for me anyway, a nice new C172 is the best. Great for trial lessons with Granny in the back, stable yet sporty and loves a field beat-up!
I had a share in a PA28-235 in '95 but was sold on the injected 172.