I did part of my training in a classic C152A and the last part in a C172 Nav iii with glass cockpit.
Most of the training in the C172 was done with the Garmin 1000 powered off so you'd need to use the backup instruments, which are like any other classic plane. I don't know if that would be the case in your school too.
In my airfield at least, all the new planes are coming with G1000 as all the old Cessnas from the 60s or 70s are getting retired.
I have flown PA28, C172, C152A, Cirrus SR20 and Tecnam P2002...I have loved all of them either with or without glass cockpit.
From my point of view, it is easier to go from glass cockpit to classic one than the other way around.
It is really up to you (and your budget), just choose whatever you feel more confident with.
Once you know how to fly, you pretty much know how to fly any kind of light aircraft with a bit of adjustment.
My advice would be: fly as many different planes as possible.
I personally don't like PA28 Cherokee. But that's just my own personal opinion :-)