I'm in the same boat as you, and the sensitive skin on my inner thighs weeps for you. When I was 30 lbs lighter, my thighs just played nicely next to each other on runs. Now, they constantly rub and wrestle with each other. And longer shorts still ride up and find their way up my thighs to my connecting region (and all the bunched up fabric becomes like a diaper). Lately, I always run in my tri shorts. I haven't tried running compression shorts, as I assume they're the same thing. They keep my thighs nicely separated and in their own confined area so everybody gets along nicely.

And teigyr, I've been there before. Everybody's happy until the water hits and then you've never had such pain. Funny how chafing works.