if you're going to the trouble of building yourself, you'll want to pick the best
(subjective reasoning) equipment for your style of riding, as well as your budget.
price is not always an indicator of durability - $$$ could be for the label, or the
high-tech materials required for extreme weight savings. some of the older,
so-called obsolete equipment is still available NOS on ebay or in dealer parts bins,
equipment that will last forever with regular maintenance.

i tour with plenty of luggage, so saving 10 grams on a derailleur is insignificant. i
select components based on heavy-duty construction, and ease of maintenance.
fewer moving parts means fewer potential failures.

basic components: xt derailleurs, suntour thumbshifters (mtb) or campy downtube
levers (road), xt or sugina-at 5-arm triple crank, xt (un-72) bb, any old generic
platform pedals with cage/straps, xt cantilevers, xt levers (mtb) or
dia-compe levers (road), phil wood hubs w/sun rhyno lite rims, 36 3x (mtb) or
48 4x (road) pro-built with dt 2- or 3-butted spokes, in/out rings alu, center ring
steel, 7spd freewheel, cane creek or xt or orbit sealed headset.