I enjoy teaching in the Tomahawk; roomy, great visability, good control/instrument layout, easy to fly. It's a good "Private Pilot take your friend for a trip in the training area aircraft". Problem is though that it really is a one performance aircraft. (Realistically) it has one take-off, one climb-out, one approach and one landing configuration. That's all that the Tomahawk's wing, flap & power combination can offer.
Students should get the whole picture during their ab-initio training, something I believe only a high wing, slotted fowler flapped aircraft can offer. And if the C150/152 is too cramped, a C172 is only a few dollars extra per hour.
I'm not sure what the case is elsewhere, but in Australia when a young low hour commercial pilot does the big trip to the bush for that first job, the check flight won't be in a Piper...