As long as the car is under warranty, the rear axle problem in the Mirage is more of an inconvenience. If it's bad, the dealer will replace it with a new one. Problem solved. You can always have it checked before you pay for the car.
Be aware that the Fit can have the SAME rear axle issue the Mirage has. So if you get one used, make sure it's still under warranty OR have the seller provide you with a 4-wheel alignment printout prior to purchasing the car.
What is your primary purpose of this car...and do you want a car with a manual transmission? You looking for cheap, reliable transportation? Is good fuel mileage the most important factor? Do you want something fun to drive? A Mirage GT only comes with a CVT. I've never driven a CVT Mirage, but something tells me that the last words you would use to describe it are fun and/or peppy.
From a pure "fun to drive" standpoint, a 1.0 EcoBoost Fiesta with a manual transmission (a somewhat rare beast) probably wins hands-down of all 3 cars you mentioned.
__________________________________________
View my fuel log 2015 Mirage ES 1.2 manual: 52.2 mpg (US) ... 22.2 km/L ... 4.5 L/100 km ... 62.6 mpg (Imp)