If you had to pick: Myrtle Beach or Hilton Head
 

I've never been to the SC beaches and am considering these two due to the Marriott Villas there.

How do they compare vis a vis each other? I like to sit at the pool, walk on the beach, ride bikes and kayak.

Your expertise is much appreciated!

I have not stayed at the Marriott properties but have been to both beaches.
Myrtle beach is a very busy beach area with lots of activities, shows, dining,etc....
Hilton head is quieter, but has good dining.
Both have mini golf and stuff to do. I found Myrtle to be a crazier place with lots more people on the beaches and around the whole town.
I just read tonight on another post that the Marriott property in Myrtle is newer.
Our family enjoyed both places. I would return to Hilton Head. I doubt I will return to Myrtle beach.

The Marriott in Myrtle Beach is in a very nice and quieter location.
Hilton Head is nice, but it's more of a retired golfer's place.

I disagree with Egret. I think Hilton Head is much more of a young place these days. Beaches are okay but can be kind of murky sometimes. Wild Dunes near Charleston is another very nice place but I don't know if there is a Marriott there. You can ride bikes everywhere in Hilton Head though!

I prefer staying in north Myrtle Beach to central Myrtle Beach proper, quieter. Most roads around MB are very busy and I would not be comfortable riding a bike for most of it. Hilton head is more bike-friendly, I think. I always recommend a drive to Huntington Beach state park, about 15 miles south of MB, for long stretch of unspoiled and uninhabited beach.

Hilton Head is more of a family beach vacation place. HH does not have a strand type line up of hotels on the beach. Several of Marriott's properties in HH are not on the beach.

If you have kids who are expecting water parks, miniature golf and amusement, none of that is at HH.

HH does have nicer restaurants, shopping and a more tropical atmosphere with the residential streets in the plantations overhanging spanish moss.

Myrtle is the ultimate kids beach vacation. Lots of family stuff to do. Casual family restaurants. And everything reasonably priced.