Full IC take over - normally you conquer territory and annex a country you get only 20% of the IC value for non-core (ones you dont have claims on to start with) provinces. So taking this option will really boost your IC. Useful if you are a small country, but unnecessary if you are a major like Ger, USA, USSR...
Tech team take over - this will allow you to add the conquered county's tech teams to yours, giving you a potential big boost in tech research. Again, useful for a small country with poor tech teams, but no great value if you already have good techs. IIRC there is a bug with this.. but cant remember what it is. Think it has something do with liberating a country that you've annexed and that causing problems potentially with teams that are already assigned research projects.
