These are two very different cars. At an architectural level the Fusion has a transverse engine and front-wheel primary drive, which means a big lump of weight is concentrated on the front wheels. I don't like transverse engine cars, because I don't like the way they handle. I've also never driven a FWD car with steering feel I like. I wouldn't worry about the longevity of the turbo engine, but I'd use synthetic oil and change it a lot (like every 5K miles). The Fusion is also a lot bigger and heavier than the Bimmer, so while it does look cool (I agree), and the ones I've been in have been made well, they are not sports sedans. Ford does offer an AWD version, but AWD never fixes basic architecture issues, like most Audis have too. Ugh.
The BMW is a rear wheel drive car with 50/50 weight distribution, it's a foot and half shorter in length, and it weighs a lot less. It has an 8-speed automatic to the Ford's 6-speed. I think the Ford is actually made better, but I like the BMW's engineering *for driving* a lot better. The new electric steering is said to have less feel, but it will still beat the pants off the FWD Ford. In my experience BMW reliability is highly variable, and I've have bad and good experiences with them. BMW dealers can be a PITA.
I'd pick the Bimmer in that comparison, hands down, but for about the same money you can have a Ford Mustang and a lot have more fun than either one, or your Mazda for that matter. Even the base car has 305hp...