KATFIVE, Jeff Masters said this on his Weather Underground blog:

"I expect that the area of extreme storm surge from Rita will be less than Katrina's, since Rita is a smaller storm."

That said, I don't know to what degree Rita is smaller. I suspect that now that she's more or less through an EWRC, she'll continue to get bigger. Whether she reaches Kat size, I dunno.

I'd like to find something that would let me compare them (and other storms like Charley, Dennis, maybe even as far back as Camille), preferably graphically, but I don't know of any such thing yet.