Ebbie 2003.
I didn't find landing either planes particularly challenging... Yes it feels a little different, the view outside is a little different, the flare is at what appears higher or lower depending on the type (and perhaps interior). But overall they are very docile, and relatively easy to fly planes.
Passengers I have flown seemed rather indifferent to flying in either the 172 or the PA28. I occasionally flew both the same day, and found the split between which passengers liked which plane most depended more so on the comfort of the seats than anything else.
Re: Spins - all the C172s and PA28s that I have flown in the UK have placards stating "Spins Prohibited"... Then the POH states "intentional spins prohibited". I have had spin training in an Extra200 (which was really fun to fly actually - at some point you should give that a go Tobster - so much more fun than the Cessna / Piper / Robin / Beechcraft I have flown thus far for local play...).