I owned a Yaris for 5 years and like a couple of the posters above never had a days problem with it, and that was doing 20k miles a year commuting, both on motorways and backroads.
I've driven a couple of the new model Micras as rentals and found them a nice car to drive, easy motoring but a little more tinny (for want of a better description).
I'd go Yaris everytime, as an aunt who occasionally moved nieces around, babyseats fit easily, with little need to move seats around, and the buggy that my sister had fitted well into the boot (against that another friend bought a buggy that wouldn't fit in, so its not just the car you need to evaluate).
as a side note, having just moved up to a salon car, I find I miss the many cubbyholes that were in the front area of the Yaris.... for me its weird to be back to a basic glovebox, after having 2 x glove boxes, an underseat drawer on the passenger side, an under steering column space, plus the 2 spaces either side of the console!