(I waited to see if anyone gave an answer I agree with ! No one did, Ha!)
Here's the deal... (as compared to under the bb shell guides):
- They accumulate dirt and goo in the crevices that are extremely hard to thoroughly clean/and potentially rust. (It's actually hard to thoroughly get paint on them with all the angles and hidden areas.) - Many (!) are improperly brazed on, as to position & how they direct the cables.. A savvy frame builder can point out that immediately and novices are blissfully unaware. - They are heavier (OK, not by much, but nonetheless...) - The chain stay stop often gets whacked, and chipped by the chain.
I still like them, but under-the-bb-shell routing is easier, no question. And "more modern!"?
Dale Brown
Greensboro, North Carolina? USA