In my personal opinion, the upgrades from the first game are better.
With archers, the upgrade that lets them ignore a bit of armor is not to be underestimated. With the good damage and fire rate, ignoring armor lets them deal with dark knights quickly and easily.
Not much to say about barracks. I will say that increased rally point range is handy.
The slowing curse on the mages is AWESOME. Cutting enemy speed in half, even momentarily, is pretty major. Not to mention the upgrade that lets them destroy armor.
I feel like the lack of cost reduction in frontiers really cut down on potential for artillery. The cost reduction really comes in handy due to the large cost of artillery. The upgrade that makes them do the same amount of damage to all enemies caught in the splash can also let you do tons of damage to the horde.
Most of the upgrades for reinforcements and rain of fire are the same between versions, so I won't talk about them.
What are your opinions?