Does avionics type matter when training for PPL?
The answer is going to be along the lines of "it depends" but in all honesty thats not what you should be basing your decision on when it comes to training schools! Meet some of the crew, see who has better facilities, and which you get a better feel for.

In any case, your PPL training will simply teach you to fly an airplane, and all the associated things such as navigation and airmanship - the type of avionics the aircraft has installed is pretty much irrelevant.

When you get your license the commonest small aircraft at most airfields have traditional avionics, so you'll want to be familiar with them - if you do happen to train with a glass cockpit at most you might want an hour or two with an instructor in a typical small airplane.

On a personal note, and maybe im a bit old fashioned, but I think you should understand how a "gadget" works before using it. I like to see a physical VSI, AH and altimeter. I like turning the little Knobs and manipulating proper buttons in an airplane. One thing I can say for sure is the first time I sat in front of a glass cockpit I knew what everything was, what those displays were telling me. Would the same happen if you'd only ever flown a glass cockpit and got into a 1970's C152? Possibly - I don't know.

Good luck with your training.