As a Marriott Platinum, I would recommend Hilton Honors. Point accrual is far superior ( better bonus opportunities, website booking bonus, etc.)and upgrade rate is FAR superior in my experience. I am a comped HH Gold and have had a far better experience as an HH Gold than as an earned MP.
I have also found CY properties to be on the decline with horrible beds while Hamptons are usually cheaper and more comfortable. Among full service Marriotts vs. full service Hiltons, I would give Marriott a slight advantage on overall quality but Hilton has a huge advantage on upgrades.
I have no experience with Starwood but there are several here that swear by them. Good luck.