Thanks for this calculation. I agree, its a close thing.
Apart from the points, what else would I be losing out on with a redemption? There won't be any upgrade at a Hampton anyway, and breakfast is included.
I have a feeling I'll want points for NYC next year. That's selling at 280K points for five nights for this year's marathon.
Anyway, 30K points will get me at least one free night in most provincial cities in the UK.