I sold my 1980 P125X (not PX125) last summer for £600 as it was sitting in the driveway doing nothing...
My brother spent £2.5k restoring his 1964 GL including a bare metal respray, 12V electrics and a larger replacement engine . It looks beautiful but the engine siezes periodically when it gets too hot (last time on the westway fly over) so he may be looking to get rid of it.. he uses it to commute to work on.
Vespas are great fun for pootling about town with excellent tight turning circles and light weight - their performance and high speed handling is appalling and the brakes are comical to dangerous on the older drum braked variety I've ridden. Pre restoration/rebuild, my brothers GL would struggle to keep up with traffic out of the lights, has no indicators and an oval front drum (now replaced) would lock the front brakes if you so much as breathed on the lever. My PX was a much better performer but would refuse to tick over in heavy rain and the brakes in the wet wouldn't even lock the wheels.
One of my staff bought a reconditioned 1970 150GS (I think) and got through clutch cables every two weeks and spent relatively a lot of money getting the transmission rebuilt.. He was a big chap at 6'4 which may have put extra strain on it..
Then there is the faff of changing plugs all the time when you oil it up in the cold, messy garage forecourt spillages with 2 stroke oil and a small jug full of oily tissues..
No doubt a finely fettled example would perform as it was designed.
So in short, if you want a fun commuter you don't mind abandoning at the side of the road occasionaly, buy a vintage scooter.
If you want to go anywhere on the open road and crave performance, comfort and handling, stick to proper bikes.
Having said all that, if I had a garage, my PX would still be in it, they are just so cool for bombing around in a cloud of 2 stroke smoke on a sunny afternoon, cost nothing to run and make you feel like an extra in a Fellini film
Ade