Well, I'm not sure you supplied enough information, so I'll ask a few questions: what are your priorities? What are you looking for in a car? I assume cost in irrelevant in your case -- is this ture? Is performance important to you? Safety? Fun to drive? These two cars belong to different segments -- the Mondeo is a saloon car and the 5 is a minivan. Do you need the extra space? Can you test-drive the cars before you choose? Maybe you just won't like one or the other.
The Mazda is quite fast for its class, handles OK, rides OK and is quite practical. The Mondeo is a bit slow, handles very well, rides well, and I will probably be practical enough for your needs 99% of the time.
The botttom line is probably this: If you're more of a family guy, get the 5, and if you like driving, get the Mondeo. I'm pretty sure you'll be happy with either of them.