Poppa, from my point of view it's all about different flavours of tone; chocolate or vanilla are both nice!
There has been a perception in some quarters that rosewood is, somehow, a 'superior' tonewood. This is manifestly not the case; I have often played high-end rosewood bodied guitars which, quite frankly, were dogs. The same applies to mahogany and, of course, the converse is true.
The fact is that there are superlative guitars, average guitars and pigs regardless what they are made of.
I currently have guitars in maple, rosewood and koa; all sound great and very different from each other and none is 'better' than any of the others.
You are forunate to have such a classic and iconic guitar in the D-18. I have owned many Martins and the plain vanilla D-18 was among my favourites.