The average low is +11 deg F in his town. I'm sure we'd all agree that "average low" is just that; there are days it's warmer and day's it's colder. That town he's in is only 4 deg F colder than Billings, on average. And only 7 deg F colder than where I'm at (central IN). In fact, nearly all the record lows in his town are only in the -30s. I understand what your saying, but I don't agree that its so darn cold that synthetics are a must.
UOAs show that a large difference in base stock does not manifest itself into a large difference in wear protection given the temps he's seeing. I point this out because your first post in this thread was asking about the CCS and MRV of the two products and how they contrasted in cold temps. Your quest, in essence, was a "which is better" topic. The two oils will react a bit differently, but the wear protection they provide is (statistically) going be be the same. If my dino oil can protect against wear as well as a premium syn, then the comparison of two syns are going to be very much the same.
I see this type debate so very often here; people get all frenzied over the oil and debate nuiances that simply do not matter in the long run. Which is more important; knowing the line-up roster of a ball team, or knowing the final score of the game? Same goes with oils. Don't get so caught up in which oil has what additive or base stock. Look at the wear as predicted by thousands of UOAs. Knowledge of MRV is an input; wear data is an output.
Let's suppose for a moment that there was a wear difference of 10% between the two oils you mention. (I do not for one second believe this to be true, but I'm making a point here). If the "inferior" oil come with 10% more wear, then wouldn't that mean 10% less final lifecycle? If his engine is good for 400,000 miles, then it would be "only" good for 360,000 miles with the lesser oil. Is your buddy ever going to drive that far? Only people who drive lots of hours every day ever rack up that kind of mileage. And if that were true of your friend, then "cold starts" are not a major concern for him because he's going to be at full temp for the vast majority of the operating time. Or, the opposite is true; he may only put 200,000 miles on that truck, if even that, and it would take him 15 years or more to ever get to half of the lifecycle of the engine. In that case, why even worry about it; there is a HUGE potential for the vehicle to be stolen, wrecked, or just plain traded in before the engine would give out from the "lesser" oil. Simply put, it is silly to worry about wear unless there is a reasonable expectation that one would actually reach the finite end of the lifecycle. If that is not a reality, then the topic of wear is moot.
If wear is not an issue, then one can at least debate the "ease" of starting. You say you don't know which engine he has, but we can at least know that the 7.3L, 6.0L use HEUI. That in mind, a thinner oil is going to aid in quicker revolutions for starting compression, and will quell (or at least reduce) the dreaded "romp" of HEUI in PSD engines. I know of a few guys that run 10w-30 and one that runs 5w-30 in their PSDs. We all agree that there is little difference between the two choices when it comes to cold starts, but we also agree that the 5w and 10w do outperform the 15w products on cold starts. In essence, the HEUI systems seem to prefer thinner oils.
Here's what I see as a factual basis for this discussion:
* It's cold where he's at, but not stupid-uber-ugly cold like what is seen in the upper northern part of this continent
* At the temps in his area, any 5w or 10w oil is going to do just fine, and countless UOAs prove that
* The two oils you mentioned are very likely going to give the same wear protection, regardless of the difference in MRV values
* You can get your friend a great deal on some nice PAO oil
* He should buy whatever oil he darn well wants to; that's the only way he'll sleep well at night