Tom,
METT-TC dictates, of course. I chose foot troops as that has shown the most gradual changes over time (3,000+ years is the scope I'm looking at), and one of the patterns I think I'm seeing has been most prominent in foot soldiers. Let me gather a few more responses before I get into that, so's not to pee in the information pool.

sometimes technology passes from use because of stupidity
Stupidity is overly broad. The specific stupidity I can point to several times from the late Middle Ages to present is the facination with 'new' combined with a short-term conservation of resources. In your example of map & compass, the 'bright and shiny' was GPS, the resources conserved were training hours (and indirectly dollars).

Another example would be the transition from crossbow to matchlock. The crossbows of the early 1400s were functionally superior to the matchlock in every aspect, but relatively expensive. The 'new' was gunpowder arms, the resource conserved was ducats (directly in this case).

Comm gear offers some interesting examples of success and dead-ends, like the civil war teletype, the Napoleanic semaphore, and the heliograph of the British Raj. And again, METT-TC had a big vote in each of these systems.