When you consider an engine all you should care about is TOTAL cost of ownership.
1 Fuel economy, you won't spend more on anything else than fuel. Think that 2/10ths of a MPG isn't important over the 4 or 5 year life of the truck? If you didn't answer yes......
2 Maintenance. How much oil does it need? How expensive are the filters? How often do you need to service it? Does it need any other special maintenance more often than the other guy (valve set, emission control parts that need replaced etc.)
3 Cost to put a particular brand in a truck. Sure brand x offers a great warranty and the service is good, but if it adds 5 grand to the cost of the truck are you going to get it back? IF you said yes, are you prepared to incur the downtime? If you think your going to need 5 grand of warranty work done in the 5 year life thats a crapload of downtime that isn't free. If you think that it will save you that much in fuel or cost of re-build (if you keep it that long), different story.
4 Cost to re-build, if you've decided that keeping your truck for 10 years is a smart idea, are you going to have to do an inframe? Don't ask the sales guy how much it will cost, go ask at another dealer.
5 On road support, all the warranty in the world won't help you if you are in Buttmunch Idaho and the closest dealer is east of the Mississippi.
6 Parts availability, OK so there is a dealer in Buttmunch, but if the water pump has to come in from Lower Uzebekistan your going to get awful tired of the food at the only restaurant that Buttmunch has. And, if you think your safe on this one because you have a common brand of engine, how common is the model? Water pumps for a 15 liter might grow on trees but you have a 12 liter. Tired of the buffet yet?
7 Performance, sure is a long way down the list isn't it? It has a lot more to do with how the truck is spec'd and your driving than anything else. It is important....because it affects number 1. If you end up driving it a gear down because it feels gutless in the top cog, say goodbye to fuel economy. Some say horsepower only costs you if you use it. True if you are 100 % super duper professional driver all the time. How many of you are that perfect? I see one hand, and I'm sure he's not super human like he says. For those of us in the real world, the 600 hp engine will almost always cost you more in fuel (notice I didn't say MPG) than the 400 hp engine.
8 Resale Value. If you are going to turn your truck in fairly frequently (less than 4 years) it might fetch you more if you have a "popular" engine, but if your going to be 10 years out, the difference between a 600 hp monster and a Briggs and Stratton ain't going to amount to much and besides, who did you buy the truck for? Yourself or the guy you're going to sell it to? The resale argument is pretty weak these days, as fast as technology changes so do peoples preferences. What is popular in resale today likely won't be in 4 years.
I'm reasonably feisty tonight folks so I welcome your comments!!
By the way, there are some big fleets that don't get it right, nobody gets a hole in one every time out. No one can spec a perfect truck, there are always trade off's you have to make. The important thing is to at least make sure you've thought it out, not made your choice based on emotion or what you heard on the CB.