I did the opposite. Went from renting a 172 for most of my landaway type flying to buying a share in a Warrior. I still like the 172 though.
As FFF says in his post - if it's going to be suitable for the sort of flying you want to do and it's as nice as you say then do it. Nothing beats the flexibility of having a share in your own aircraft and even though the 172 is 5-10kts slower than the PA28 it has its pluses too. A demonstrated x-wind limit of 18kts verses 17kts (not much - but hey, it's better) and an incredibly slow approach and landing speed. If you want to get in and out of short interesting strips and airfields that's the aircraft to have. If it's got the long range tanks fitted too you'll find the only limitation you have is your bladder - not the aircraft.
If it's that verses a tatty rental whenever it's available, with the subsequent limitations on how often you can take it away then go for the share - and enjoy your touring
(You'll get a lot more distance for your money too don't forget
)