It depends on your budget

for me, best hotel in Koh Samui is Poppies and best hotel in Phuket is The Surin (average rate 250€/night )

when you try both, is difficult to choose something different then 😃

Poppies for me is something like a drug (Bali one also) and The Surin is one of the really few hotels with something like private (and wonderful) beach in Phuket (not really far from Patong)

if both are on your budget, don’t think other options

if not and/or you want to stay at an Accor, There are lot (especially in Phuket) of options, depending where you want to stay. I would suggest you near chaweng in Koh Samui and not far from Patong in Phuket, if it’s your first trip to both places

agree with Chinnoylad...I wouldn’t travel on Samui and Phuket both on same trip...but it’s a personal choose

i would choose Koh Samui or Phuket + Chiang Mai