I've been to both resorts, though I haven't been to the Surf Club since 2006, I have been to St Thomas each of the last 2 years.
The Surf Club has the really nice pool area with Lazy River. It has the 3 resorts right next to each other, the Surf Club, Ocean Club and Marriott Resort, so the overall complex is quite large, and I thought felt more crowded. The Surf Club has a much larger and nicer beach than the Frenchman's Cove, though at the Frenchman's cove you can go over to the Marriott's beach which is nice, but not as nice as the Surf Club. Nobody really hangs out at the Frenchman's cove beach, everyone is by the pool, whereas the Surf Clubs beach is packed, which also makes it extremely difficult to get a palapa on it.
St. Thomas is much more scenic than Aruba as it is more lush and mountainous where Aruba is flat and a desert. The water seemed to be warmer in Aruba (though check this out for certain as I did go at different times of the year), however the water in St Thomas was more clear, though the water in Aruba was pretty clear as well, just not as clear.
Statistically, Aruba is more safe than St. Thomas, though as the local experts will definitely point out, St Thomas has been safe for tourists. Also, depending on the time of year you are going, Aruba as a general rule does not get affected by hurricanes where St Thomas does, and has had close calls each of the last two years when I was there.
I personally much prefer St. Thomas. Aruba was great, just not much to see outside of water activities. Last year I had the choice between Aruba and St. Thomas, and even though it was Hurricane season I chose St. Thomas. Incredible water, nice beaches, great scenery and access to St. John and the British Virgin Islands make it the choice for me.