Here's a good write up from Russ Roca and Laura from Path Less Pedaled of their mountain double (aka Touring Double) and the reasons why they went with a double rather than a triple.

I met them at the Pedal Expo in Oregon last year, incidentally shopping for a Salsa Vaya and coincidentally discussed touring doubles with him. I'm really glad he agreed with me on this and enjoyed riding it as the review suggested he liked it! Noticed they are riding 42/28, not far from 42/24 like mine.

http://pathlesspedaled.com/2012/12/s...-vs-surly-lht/