I think the UNSC are better even though i prefer the Covenant, the UNSC play more like an RTS, quick access leader powers but with a price and descent time limit, upgradeable super units and spec units, and they get better the longer the game goes on like an RTS should.
Covenant on the other hand, super hard leader units that require all attention on them in order to use them effectively and without them leave the army more often than not struggling, crappy spec units (although the honour guard are pretty cool) and no super units AT ALL! PLUS your basically forced to rush in order to win as they dont really get much better later on hence why they are at the top of the boards, rushing is the bane of this game cus it works too easy and loses the whole idea of multiple strategys! the lack of focus needed on your base means you can just spew out troops and mob the enemy, wheres the strategy there??? why even bother going into the detail of upgrades when they can win with a few basic units within 5 minutes!?
They should have created the Covenant similar to the UNSC and had a sortof NOD vs GDI thing going where they build and use fairly similar but have very unique differences making gameplay much more satisfying win or lose!
Oh and the Covenant have the same pop cap as the UNSC (+10 upgrade) and marines costing the same as grunts...what the hell!?
I have really tried to enjoy using the Covenant for preference reasons but i cant, i hate rushing, theres no satisfaction in it and couldnt care less about being top in the leaderboards, all they can do is rush 1st and if it fails either resign or build counter units and hope to survive as most counter units available in the limited pop cap are crap against buildings leaving you unable to retaliate before they rebuild. in 2v2's etc maybe more of a chance but i like to know i can go 1v1 and survive and comeback on my own, i will probably stick with UNSC now but cant see the point in only using one army in a RTS. In StarCraft i used all the forces, same for C&C but in this the Cov jus arent set up as RTS material!
Live By Honour, Kill By Stealth!!!