Q. Both the FZ 25 and FZ Fi V3 have the same milage even though the FZ 25 clearly has more power which one should I choose?

First of all You have a wong assumption about mileage, FZ25 provides you a mileage of 35kmpl-40kmpl in cities whereas FZfi V3 cn provide gou a mileage of 50+kmplIf you want aggressive riding go for FZ25, if you want Decent and more comfortable riding go for FZfi V3Note: Gear shifting is little bit harder in FZ25 which may mak you uncomfortable during heavy traffics

150cc engine are not that good for long rides...if you are buying for city rides buy FZ Fi V3 for touring and city rides buy FZ 25

Depends on your preference, both can be used for city ride, but fz25 is always good for a highway mile munching