Do yourself a favor and finish your Private in the plane you soloed in.
Remember, your solo sign-off is a type rating! That means you will have
to be signed off for solo for each type of aircraft you will fly. C150
and C152 require a sign-off for each.

Once you have your PP certificate, then you can get checked out and fly
any other single engine aircraft.

Meanwhile, if you change over to a Piper Cherokee, you will have to
deal with fuel management, IN FLIGHT. You have to turn on/off a fuel
pump in the pattern, switching of tanks (can't select both, only left
or right or off). And you will have to re-learn to taxi and what the
sight picture is for landing.

Switching between a C150 and a C152 is pretty easy and I did that
during my training (and had to get a sign-off for both aircraft for
solo). I much preferred the C152 and took the check ride in it.

BTW - I own a PA28-180 today. When I bought it, I had about 200 hours
in Cessna hi-wings. Transition to the low wing Piper, in my opinion,
would have cost me another 5 hours minimum (for solo). Today I have
over 130 hours in the PA28, done in 18 months (the first 100 were done
in 7 months, but here in OH with all the nice winter weather and the
annual from hell...).

Later,
Steve.T
PP ASEL/Instrument