It was considerably cheaper to insure my car in my name - probably due to my greater driving experience and other factors. In the case of my wife's "runabout" it made no difference (a couple of quid IIRC but I can't remember which way). My wife refuses to drive my "tank" (as she calls it) but, by having her on my insurance, she can if she wishes. I do occasionally drive her car though.
We're both a bit over 30. :-p