Smooth, lowest friction arc, in order to achieve this , a bit longer is better than too short , particularly as Indexed shifting is fussy about the friction
between the command lever on the bars, and the action at the rear..

the cable routing down the seat-stay may offer a straighter line than one from under the chain-stay ..

so where the braze on stop is on your frame is a variable. preventing a Rote answer. It in the end, Depends..