I have owned the Honda CG 125 2021-22 and the Unique UD 125 2021, which were bought brand new. The major difference people aren't aware of is almost in every aspect be it wiring, rubber parts, shockers, clutch plates etc. The Chinese one given its price is okay but Honda isn't that great either. With care Chinese will serve you well for at least a year or two with timely oil change, brake service etc depending on your mileage. I won't advise going for a second hand because people here buy motorcycles to abuse them which makes your life miserable with frequent visits to the mechanic. Even if you go for one replace the parts with Honda when it is needed.
