With many hours in both 172s and PA28s, I really don't have a strong preference either way.
The 172 is a little harder to get trimmed out than the Cherokee, but once you do, it flies like a dream. The Cherokee is more solid in flight.
On the ground, the 172 wins big points for TWO DOORS and a rain-shelter wing. The Cherokee wins in the air for the low wing, and the airliner-feel to the power quadrant.
Cherokees once again lose big points for the single-door system, which I find awkward and indeed compromising safety, but when flying by myself I simply fly them from the right-hand-seat.
I did my PPL in Cherokees, then hour-built in 172s. Did the CPL flight test in an Arrow (PA28), and now am working in a GA company with a fleet of both Cessna 210s and PA32's. Same complaints and compliments about these aircraft as the four-cylinder versions - otherwise identical.
I dont care anymore which aircraft I fly - the Cherokee and the 172 are so very very similar, but the choice on the day should be dictated by the requirements of the flight, and the availability on the field.
Safe flying