well..... i gotta say to you to u tht nice choices both are very good cars.....i just wanna tell u, u dont have to worry abt maintanance costs, i mean u will get atleast (depending on the company) some number of years whereby u will recieve free maintanace....

but according to me here are the plus and minus of both cars.....

Mazda 6
PROS:
.good zippy engine, and very nice performance and excellent road manners
.a very comfy sporty and attractive interior

CONS:
.kind of cramped interior when compared to the Galant
.not much of a resale value, and probably the only the Ultra V6 can be compared to the size of the galant

Mitsubishi Galant
PROS:
.nice roomy interiors and far more comfortable than the mazda 6
.bigger payload capacity in the trunk

CONS:
.not so good road manners, and lest its the v6, the 4 cylinder is only average
.bland interiors and plasticy feel inside.