Fasteners are complex beasts that comprehend a family of technologies to apply, design, evaluate, and fabricate. It is a particular area where I'd not say I'll never do or use X.Each has their respective place and purpose, and personally I would not use loctite where a locking fastener is called for. I'm not an engineer and as you note MB knows what they are doing, so it's a bit illogical to think they wouldn't specify one over the other for a functional reason.
Locking fasteners can be pricey...but unintended disassembly is decidedly more costly.
Perhaps you are not aware but thread sealant products, among which are the Loctite's, come in quite an assortment of varieties which run from the ones for fasteners to be disassembled without effort, to those that may require the heat of a torch to loosen up the mating threads (e.g. Loctite blue). The problem with liquid fastener locking products is that they may need to be applied by hand and/or that they may contaminate an incompatible joint or assembly.
As for the other varieties of self locking fasteners, the teethed washer head screws or nuts are the most dependable, from a reusable stand point. Deformed thread fasteners, or those with locking inserts, is worth to replace them whenever we take them apart. So, it can become expensive if instead of purchasing them at a shop like Universal Fasteners, or McMaster Carr, you purchase them from your local stealership. Whichever way you go, make sure the markings on the fastener match or exceed the ones you removed.
Cheers, JV :thumbsup: