Hi tinylion...we've been to both...the resorts are worlds apart in atmosphere and locale. We enjoyed SEB much more than we did SRB, but that all comes down to personal preferences.
SRB is close to other amentities including shopping...just a quick jitney ride away and you can be at the straw market and downtown for shopping, or you can visit some of the casinos. The resort does not have a great beach but does have a very nice offshore island which is shared with cruise ship visitors (wasn't an issue when we were there). SRB is not one of our favourite Sandals, but that is based purely on personal preference and a few negative experiences we had (this was 4 years ago and the resort has seen manangement changes since then). I recall the food as being good to very good.
SEB is stunning! It is a former Four Seasons and so I would consider it one of the more elegant Sandals. It also has a Greg Norman designed golf course if golf is of interest to you. If you are looking for a quiet relaxing resort to spend quality time together, this would be the place. The beach is fantastic and the pools are wonderful. We were there in March...here is the link to my review in case you find it helpful:
If you wish to see pics of SEB to help in your decision, feel free to send me a PM and I'll send you the link to my Picasa album.