There are quite a few differences between wood and D-RAM. Wood looks better and it's lighter, but it also costs more. Both of these constructions are pretty strong - the d-ram is a bit stronger than wood when your mast chrashes into the nose of your board, but i find the wood to be stronger when you land a jump too flat or when you over-rotate a forward. But when it comes down to reparing the boards, D-ram is easier to repair in terms of looks, because you just spray on the paint. Matching the wood colour can be quite a difficult thing to do.
In the end, it all comes down to personal prefference - decide on what is important to you. If it was me, i'd pick wood.
As far as i know, with an s-type you CAN'T go wrong