Flown both the tomahawks and C-152s. Prefer the tomahawk hands down mainly because of the extra room (I'm 6"1' and struggle into the 152 but have no problems with the tommy)
They're also quicker, have excellent viz and are excellent for teaching stalls as they'll bite if ailerons are used!!
Operating costs are around about the same as a 152 I believe.
However, a tomahawk is not certified for any type of spin training, in fact from memory it is prohibited.
They're even better value for money if you've got Warriors to move onto for Navs etc because of the near identical cockpit.