Learned on C172 and now own a PA28-181 Archer II.
I am large (not tall and 20 stone - always amuses me when I see the "I didn't know fat blokes could be pilots look") - the Cessna is certainly easier to get in and out of, but the PA28 is not difficult when you're used to it - the trick is to slide the seat back!
In my opinion the PA28 is easier to fly than the 172 - I describe the PA28 as "rudder optional", it certainly seems that was compared to the 172.
I flew several 172 variants (engine sizes) when training including one with the Powerflow exhaust - they were all good but the more powerful ones needed lots of rudder at full power and always rudder in even shallow turns.
My Archer is a 180hp and needs only modest rudder at full power e.g. take off and of course rudder on crosswind landings but seems to need very little when flying even steep turns.
Overall both are good planes to fly choosing either would not be a bad decision - one thing to factor in is where you plan to rent from when you have your PPL - may want to rent the same type you learned on. Personally after I learned in Florida I returned to Barbados to find that at the time there was nothing to rent - I bought the Archer and so since earning my PPL I've never flown a 172 - the transition was not difficult - did my flight review followed by four touch and goes then a 450 mile crosscountry (my first two solo flights since getting the PPL a year earlier - I did say that the PA28 was easy to fly!)