I would say that they are different, not better/worse:
Assyria has a UB that provides extra XP when the Great Works slot is filled (and not to mention, having a Great Works slot in itself on a building that normally doesn't have it is a nice bonus). Moreover, Assyria can worry less about falling behind in science than the Huns, since the UA gives free techs from conquered cities (once per city, though, and the only techs that can be taken are ones known by the city-owner). Because of the UA, Assyria can attack for longer, take more cities, and still be better than science than the Huns; the Assyrian UA partly mitigates the new 5% penalty per city or puppet. And, of course, the UU is a beast, though it comes later than the battering ram.
The Hunnic Empire, on the other hand, has the earliest monster UU of the game in the Battering Ram, and has a great contemporary UU to support it in the Horse Archer. The Huns can start conquering a little earlier than Assyria because of the battering ram being a spear-replacement rather than a catapult-replacement, which may be crucial in some cases: getting out on the attack just 20 turns earlier can make a huge difference. Moreover, the Hunnic UA includes a production boost to pastures, which are much more likely to be improved quickly now that Animal Husbandry unlocks a trade-route. Don't underestimate the Hunnic UA. In a game where the Huns can have at least 5 or 6 cities, there's a good chance at least one city will have 3 or more pastures. Which, once improved and worked by a city with a stables, is a great early production boost because of their UA.
So, they are different, not really an upgrade or downgrade of each other. Assyria will do a bit better science-wise because of the UA, while the Huns do a bit better production-wise because of theirs. There are similarities, but Assyria gets no boost to production, and the Huns get no boost to science. And in rare cases, the extra Great Works slots may help Assyria with culture. Thus the two sides are different enough not to be completely over-lapping.