One thing to know if you're planning to rehab a deck and replace the railings (or if you're building a new deck). The new white vinyl railings that everybody seems to use are VERY THIN along the top rail -- it's not even 4 inches, more like 2 3/4". It comes either flat or curved (like a bannister) on top.
We chose to use the flat top white vinyl rail and then add a 6" (more like 5 1/2") board on top of the white rail. Be sure to use the "square shoulder" boards, not the ones with grooved sides (for "invisible" decking fasteners). I really like the way it looks, and I can use my railing-hugging planter boxes on them, too. We did have to add ADA white handrails along the stairs, because the 6" boards weren't really good for grabbing onto.
Also, the white vinyl railings come either with white balusters (the upright pieces) or with round black aluminum ones. I really like the way the black ones almost disappear to let you enjoy the view.
