I'm still a newbie, and still running the triple (Tiagra, OEM on the bike). If one doesn't replace the FD, RD, bracket, and cranks all at once (to get the advantage of shorter chainpath and narrower BB), what are the advantages of simply having 2 chainwheels vs. 3? It seems one wouldn't realize the advantages that are typically purported of using the double. I've heard some claim that a double is a simpler setup and that the chain can skip the middle wheel on a triple, but to me that's something that a reasonably competent bike owner (even I) can tune out.
Is this just one of those things that people do because the "big kids" do it, or is there still an advantage to be gained from changing part of the kit and not all of it? So far, I'm using the granny gear less and less as I get stronger. However, I've been thinking that when I do upgrade, I'd rather get a set of larger chainwheels so that my ratios are overall a bit higher, pushing me to using the middle chainwheel most of the time instead of the largest while keeping the triple (ie, make my granny gear slightly less granny).
For what it's worth, it is at least reasonably hilly where I ride, so I like the overall range of gear ratios I have and the spacing between ratios. I also like the overlap in gear ratios between chainwheels, so I don't have to constantly switch between chainwheels. I'm also thinking that even if I did upgrade, a 3x9 setup sounds like a lot less of a pain in the ass than a 2x10 from what I've been reading, which sounds finicky as hell with very little engineering tolerance.
Thoughts?