In the law reports in my country, it's simply "v", with no full stop.
Donoghue v Stevenson, for example.

You don't even say "versus" in our law reports, it's "and". Quite nice. Only problem is, a case like Me v You is said as "me and you". Just a random trivial detail for y'all.

When v isn't appropriate, I prefer "versus". Full words are better than abbreviations, in general.