Well done Dougie. Congratulations.
I have spent many years and many thousands of hours instructing in both.
I would say it matters little. you will want to try them both. they really don't vary a great deal but its more that there are Cessna people (the view down is better ) and there are Piper people ( the general skyward view is better). It really does'nt matter a great deal in the end, just a matter of choice. Try both over time and find out which you like.
Personally , like you, i learned in a 150 (well in fact before that my basic training was in a tail dragger Citabria...so a high winger), i have always preferred Cessna but for no real valid reason (if anything the cabin is possibly a little wider on the PA28 but i am subject to measurement correction on that).....
In fact, its not really a matter of Cessna =v= Piper but more a matter of whether you like high wingers or low wingers...as they handle a little differently in ground effect on departure and arrival.
As they handle a lot alike, i would try the 172 first after flying the 150. it is considerably heavier in stick forces (especially elevator, so trim is much more important than in the 150)....but just a bigger animal than the 150, and then when you are comfortable with that, try the PA28.
Go on from there....safe flying....
Gear up....