It's just my opinion but I find a Marriott Cat 9 redemption at 45000 points more valuable than SPG Cat 7 redemption at 35000 points. Again, this is due to SPG points being worth more. Also, if you look at the redemption rates of both programs, Marriott increases a flat 5k per category. However, SPG has small increments at the lower categories but then balloon to 6k-10k between higher categories.

Edit: And to clarify, when I say categories, I mean category of the hotel, not room category