Could someone explain the differences between ck2 and eu3 and the advantages/disadvantages of each?
Not really advantages or disadvantages, more like jsut differences
Crusader Kings II:
You play as a character (count at the lowest, emperor at the highest)
You 'goal' is to increase the prestige of your dynasty.
Tech advancement (AFAIK) doesn't depend on your size or how much money you put into it (since you don't put any money into it).
Economics are much simpler, you don't deal with trade. Your money comes from your demense + your vassals (depending on your laws and their opinion of you.)
There is no inflation
There are no standing armies, everything is levy based.
The map is smaller than EUIII (Europe, North Africa, Middle East)
No naval combat.
Royal marriages actually require you to have available children (and dynasty members in your court).
No explicitly Stability, it's more like replaced by individual vassal loyalty.
EUIII:
Much more focused on the State:
Your 'goal' is to increase the prestige of the state
You have five categories in which you pour money into to research.
Your money comes from tax of the State + tax on vassal states (if you have any) + trade. Money is based on tax efficiency, production efficiency, and trade efficiency.
If you mint, you'll get inflation, which slows your tech progress down.
There are standing armies and you pay maintenance on them. The maintenance level affects morale.
Royal marriages increase legitimacy/prestige (I think?) and they're limitless (besides diplomats.)
Certain actions require certain people availability (diplo requires diplomats, trade stuff requires merchants, building stuff requires.... i forget what they're called)?
This is what I think of off the top of my head.
In EUIII, the main challenge comes from managing the State. In CK2, the main challenge is managing your vassal relationships (and relationships to foreign leaders, also your marriages with regards to claims.)
EDIT: One more thing about tech advancement in CK2, it's much more out of your country, besides the use of spies to steal tech and being able to use your court to speed up research by 100%. It's much more fluid in the way it spreads. Unforunately, I don't really understand tech that much in CK2.