definitely go for it. while your 50cc 2 stroke may be peppy, a punchy 125cc will be much more so. even as a 4 stroke. acceleration and mid range pull will increase dramatically, hill climbing will improve, and of course top speed will be increased
if you can get a 150cc, better still for more mid range punch, a higher top speed, and better hill climbing ability. the increase over a 125cc may not be dramatic, but it is somewhat prominent in certain circumstances
i rode a Kymco Agility 125 this past week over some familiar roads i used to cover with an ex’s Genuine Buddy 150cc. places the 150cc scoot used to move through with relative ease the 125cc Agility had to be thrashed a bit to achieve lesser results. it doesn’t sound like much, but going up a long incline on the Buddy at 3/4 throttle and being able to hold 45 – 50mph is a lot more confidence inspiring then going up the same road at wide open throttle holding 40mph. which was the case with the Agility 125cc. of course a 50cc would probably take the same grade at 25mph or less, WOT.