What would be an approprate comparison between...

[Kai]

What would be an appropriate comparison between Roman and Medieval/dark age militaries in terms of equipment?

Reiterating Robert's point: what do you want to compare and why? Only after you defined the answers to these questions as clearly as possible you can start comparing.
It sounds self-important to say, I know, but an historical comparison between two subjects seperated by centuries is a very, very difficult affair and most people simply fail. I do not exclude me from that btw.
Such comparisons not only require expertise in both subjects you want to compare and you need a methodical understanding of how to compare. The latter is the most difficult about that. There is a great volume of essays edited by Heinz-Gerhard Haupt and Jürgen Kocka on this: Geschichte und Vergleich. Ansätze und Ergebnisse international vergleichender Geschichtsschreibung, 1996.

There is also an English article by Haupt, but I have not read it, so I can only guess from the title that it could be interesting:
Haupt: Comparative History, in: Neil J. Smelser et al. (Ed.): International Encyclopedia of Social and Behavioral Sciences, Amsterdam 2001, vol. 4, pp. 2397–2403.


My impression may be wrong, Henry, but this discussion of yours on TWC is not exactly fruitful, at least not as far I have read it (I just had to stop it...). Most I have read was people telling each other that they know about the subject and that the other does not (to put it very nicely).

regards
Kai