And, King Dain of Erebor's summon is better than the Iron hills one.
Why?
1: It is another barracks (Huge adavantage)
2:You get a-lot of unit diversity with this barracks, and you can choose whatever unit from whatever realm you want.
3: A funny thing is, this barracks has a habit of shooting arrows once you get it 8-|
So, it can act as a tower,a second/third barracks,and unlike Iron hills Dain's summon, you can consistently hire dwarves from other kingdoms.
And if you got a level 10 Dain, you won't mind the extra resources.
Another thing, (Iron hills) Dain does not summon fully upgraded infantry, so you still have to pay for that.
The team should probably change his name to Lord Dain or Dain Ironfoot; Or should I say Dain ironHead :D