There's a load of nonsense spoken and written about the Cessna -v- Piper debate.
The 172 and PA28 are both equally good trainers, they fly in kind of the same way and the 'pros and cons' essentially come down to ease of entry / egress (better in the 172) and looks (I think the Piper is prettier).
You won't go far wrong in either and picking the right instructor is a far more important choice.