I would recommend the smaller bike first, get the experience, you might find riding isn’t for you? 125s are great for learning the trade they handle well they teach you lots then, when you are ready, do your test. I have always preferred the smaller bikes particularly the 400’s easy to manoeuvre light and fast. I went for the Triumph T100 it wasn’t so much fun as the smaller bikes so traded in for a Transalp which was just fine. Now I’m 75 I’m going back to the 125’s and looking forward to them. Good luck hope you enjoy motorcycling.