I'm going to let mine weather to a silver grey, but that suits the character of my house (1956 house renovated sort of coastal/cottage/craftsman.) I'm using mangaris (red balau) which is somewhat similar to your Honduran mahogany, I think. I didn't want that new/stained deck look.

For what it's worth, there was a recent high-end renovation of a Victorian down the road, and they chose to leave the (local fir) decking untreated. It looks funny right now- much too dark and bright to my eye, on a period home, but they builder told me he just couldn't bear to do the historically correct thing and paint over that beautiful wood :)

Pics of that house:

Staceyneil, thanks for those photographs and your thoughts. Since my original post we've gone back and forth and finally decided on the following plans: we'll let the mahogany porch floor weather (silver over time). We'll paint the railings on the porch and balcony, to tie these to the 1910 house. There is a mahogany bench that we will keep stained with Sikkens -- shouldn't be too hard to keep up with that job annually, which is what the man doing the millwork recommends. I agree with you that the natural/stained finish on the Victorian house seems jarring. We'll see how that goes, and I'll post a photograph next summer.
Lynn