Important factors: what are those calories comprised of, and what kind of calories do you need in a survival situation? Just having a full stomach is not the ultimate goal.
A diet of high carbs and low fat/protein is ideal for high energy situations. It is also ideal for times when water is extremely scarce. It sucks water out of your body to digest proteins and fats. In contrast, water is actually RELEASED into your body from the digestion of carbs. This has been very precisely studied and validated by Golden and Tipton in their excellent book
"Essentials of Sea Survival".
In very cold conditions the extra energy packed in fats is certainly of great value, but you still need carbs if you're going to do much work, and you need plenty of water to digest the fat. The carbs are also the "kindling" that helps your metabolism burn the "big wood" of the fats. To be sure, native peoples in arctic regions subsist on a very low carb diet, but there is evidence to suggest they have
developed genetic adaptations to this diet over many generations.
In most any survival situation, protein itself is the least important type of food. If the ordeal lasts long enough that protein is a factor, then a jar of peanut butter or a box of Datrex will be woefully inadequate anyway. You will have to consider finding a way to live off the land or sea.
I recently finished reading Nathaniel Philbrick's
"In the Heart of the Sea" which details the
wreck of the Essex in 1820. The survivors sailed in open whaleboats for 93 days and wound up eating their dead cohorts. The survivors said they were so weak they could barely stand, let alone do useful work to improve their lot. The protein & (minimal) fat kept them alive, and it was all they had, but a supply of carbs would have been most welcome. IIRC,
Steven Callahan reported similarly.
So let's look at the details of Skippy and Datrex.
Skippy, 1.1 ounce serving:
180 calories - 16g fat, 6g carbs, 7g protein. Of those carbs, only 4g are actually energy; the other 2 are fiber.
Skippy yield, per ounce:
163.6 calories/ounce
14.5g fat/ounce
3.6g energy carbs/ounce
6.4g protein/ounce
The Datrex nutritional label is widely available on the internet but it only lists total carbs, with no breakdown between complex, simple (sugar), and fiber carbs. I called the company and spoke to one of their engineers. He gave me the carb breakdown and said that they are starting to print that breakdown on the labels.
Datrex, 1.48 ounce serving:
200 calories - 9g fat, 27g carbs, 3g protein. Of those carbs, 5g are sugars and approximately 2g are fiber, so you are getting about 25g of energy carbs.
Datrex yield, per ounce:
135.1 calories/ounce
6.1g fat/ounce
16.9g energy carbs/ounce
2.0g protein/ounce
So Datrex gives you a calorie ratio much better suited to an active survival situation, especially if water is scarce. If you are certain that your situation will be cold and stationary, Skippy might be a better choice. But IMO food with a profile similar to Datrex is a better fuel.
Of course you can come up with other foods that offer the calorie profile of Datrex. The value added by Datrex seems to be the tough packaging and long shelf life. I am not strictly a Datrex fan, but I feel there is more to be considered than just calories and cost.
I have no connection with or financial interest in Skippy, Datrex, or Amazon.