What accessories are you looking at specifically? S-works are usually the highest end Specialized products (so shoes/saddles/helmets ect.), while Bontrager makes products at all levels down to the lowest price point. I've been perfectly happy with the Bontrager parts that came on my Madone (stem, bars, seatpost, the wheels were crap but I sold them). I've also got a Bontrager computer (Node 2.1) that I am happy with, and various other doodads like a multi tool. Don't care for their saddles, but YMMV.