Hi
I am not to sure about these two.
I tried booking with the Paragon for Xmas but they just do not reply to emails, although they do seem expensive, but the Hotel looks good and the position near the beach is also good, you get a lot of sea breeze at the north end of Patong Beach so would imagine it is also nice and cool and the beach is not so crowded up there.
Can't tell you much about the Mercure as it says it is opening in November.
Look a nice Hotel though and might try and book for Xmas and New year.
Their Hotels in bangkok charge about 2,000 baht for the Xmas New year period but i would imagine that it will be up to 5,000 baht as it is Patong and the Buffalos are in town.
Hotel Grand Mercure Fortune Bangkok: book your Mercure hotel in BANGKOK
Regards
Drew