I haven't played as the Machaka, but I played against them (as Caelum, I believe) . . .
They kicked my . . . umm, my you-know-what.
Lot's of fun though. Their spider mounts will continue to fight even if the riders are slain. I'll bet they're expensive, but they put up one MAJOR fight!!! Their webbing is rough on those enemy troop lines too, and they have some powerful magic-Users to back up the spider-cavalry. Cool stuff, and next on my list to play after Mictlan. (I haven't played with the Blood Magic yet; Mictlan seems like a good choice to try that.)
Oh, and about Ulm: I've played twice as Ulm and I really like them. I think they can hold their own against anybody, as long as you don't do what I did and try to push forward on too many fronts at once! I haven't tried Marignon yet, so can't give you any personal feedback on them.