Hilton's big devaluation earlier this year effectively locks their points into that .6-ish cent value with a few limited exceptions.

Midsummer Seattle hotel rates can be spiky...if you're seeing $400-ish all over town, I'd probably spend the Marriott points. That's what they're there for.

I've stayed in all of the downtown Seattle hotels except the CY Pioneer Square. I consider them all positive representations of their brands and would probably just pick the one most convenient for you. My personal fave was the Renaissance...I became a pretty regular guest there and got to know the FDC's and bartenders pretty well.

Stayed at the Hilton Seattle once. Felt it was an "average" Hilton, which is not as nice as the Marriott properties. The only case I'd make for redeeming there is (a) you don't see yourself otherwise exploiting better uses of HH points such as a 5-night award and (b) are holding your MR points for a Travel Package.