Ordering online and choosing sizes

[HareTodayDragonTomorrow]

I want to order a skirt. Waist measurement puts me at size 10, hip measurement at a 12. Bust measurement puts me at an 8, but that's irrelevant here.
How do you choose which size to go for? I've a dress from the same brand in an xs, but that's not much help. Ordering both and trying on is not an option (tax limits, return postage etc)

What make is it? Maybe one of us has already tried it & can help.

It's this one from Lands End.

There's only an inch difference in the two sizes. The sensible side of me says get the 12 as you can have the waist taken in but then I bet the 10 would fit on good days.

Bumping really for the after work/children have gone to bed crowd.