.I would let my wife drive the Focus in this weather.

Where's Nowheels when you want her she'd love that, still hopefully another like minded lady driver will be along soon to defend their patch...:-)

It's down to the tyres as usual, when i've collected rows of identical cars from snow covered compounds those fitted with wide low profile summer slicks will not budge where otherwise identical cars with sensible tyres get about with ease.

Try feeling the treads on the two cars with your finger nails, i bet the Focus treads feel like hard plastic and the Micra's feel much softer.