Cities- take over or raze?

[Javariel]

I'm having a hard time deciding when to take over vs razing my enemy's city. Generally, I like the idea of stealing his city. But I played a very aggressive game this weekend where I went to war early on (I was on a 2 nation island- I wanted the damn island). I beat him easily, but the addition of his cities cut my income down to 60% on science, without me expanding myself (meaning there was a whole 1/3 of the island left unclaimed, and I was trying to take his 1/3). Whats the solution here- should I have razed his cities instead?

 

[aas247]

if theres forest around, and ur units are in danger, its probly better to raze the town and move into the forest for the nice bonus

 

[Tennyson]

I take cities that are near my border or otherwise valuable, and raze the rest. This way cities I take can use tiles that were already in my borders, and by razing the next layer of cities their borders can expand outward.