This has many issues I'm going to address.
Firstly: Brakes.
For me discs are a necessity and I'll never again buy a bike with rim brakes. There's just no plus side to rim brakes, none, especially in touring. Feel is worse, compatability is worse, power is worse in both modulation and control (Vees are powerful but grabby on off, cantis are weak and spongy)
You have a better choice of levers in discs because you can always use a disc caliper no matter which lever you choose. You just choose either a MTB or Road caliper.
With rim brakes you can swap to some extent but if you want Vee's you're stuck with Vee drop levers (which suck, so bad...). If you want a better fitting road lever of brifters you're stuck with cantis which are whole different level of personal agony. Travel agents are not worth it especially in a touring bike where you'd want simplicity and durability instead of gimmicks.
And tire swaps and using different wheelsets etc etc is much easier with discs.
But enough about that.
Then there's the supposed superiority of the CoMotion frame. This really boils down mostly to whether the skill of the person wielding the welding torch gives some quantifiable advantage to the frame. CoMotions are made in the US, Surly's are made in Taiwan in a factory which makes most of the steel frames sold by major manufacturers. I'd wager that CoMotion welders are not more skilled than their taiwanese counterparts. their methods can be more advanced, but that really only counts in terms of frame finishing (such as reaming and chasing etc, which you really don't need to do yourself with a surly frame)
CoMotion uses Reynolds 725 which is heat treated 4130 Chromoly and thus marginally stronger in the middle of the frame tubes (since welding strips the heat treat at the tube ends) as in Surly frames which use untreated 4130. Thus Comotion frames can be made slightly lighter as the middle buttings can be made thinner.
But the big part of CoMotion price comes from the possibility of getting a custom geometry. I've understood that their frames of the same model are the same price no matter whether you get a custom geo or not. So CoMotion socializes the needs and higher cost of producing a custom frames to people who don't need a custom geo. As much as I love the idea of custom geometry (as I think I need one for my next bike) I find this method of working slightly questionable.
Anyways I'm in the understanding that CoMotions are only slightly superior to surly frames and that's only because of the use of a better steel grade (heat treat)
I say, take the Surly. you'll thank yourself with the discs when you realize that the levers you chose suck and you'd rather sport brifters or a Sram S500 brake levers.
And the surly likely has more in its frame than you'll ever need and more. I've done 50mph descents with mine, climbed the alps, it's been banged to the moon and back and not a single scratch even showing metal yet. Man I love my LHT. Sad that I only have the front as disc and the rear is a rim brake. I now need to get Avid shorty ultimate in the rear so I can use a better more ergonomic brake lever.