"Stephanie Plum, is that you?"
Personally, I'd trust my fate to Kinsey Milhone over Stephanie. Kinsey rarely even runs a comb through her hair; she's too busy kicking bad guy @ss, LOL! ;)
I've read all the books in both series and agree, Kinsey is certainly more competent. I don't think she's ever had her vehicle blown up in a single book, unlike Stephanie, who does it multiple times in every one.
However, Evanovich makes me laugh out loud and then there's that Ranger factor. ;-)