I'm playing noble as Kathrine. I am on a long contenent on the east with Bismark on the west (toward the middle) Egypt in the north and Kublai Kahn to the south. I got very lucky with the map with horses, copper, iron, marble and stone all close at hand. I also got lucky with the goodie huts and completing the Oracle got me Feudalism. That combined with horse archers decided me to take out Bismark. (We were already starting to share a border.) When I took Berlin I discovered that he was kind enough to build the Pyramids for me. :) That leaves Egypt, who has a very bad starting position. I think I'll keep them around. We are already friendly and have several trades on going. I'll convert her to my state religon and let her expand through the nothern tundra and fill up hte space against expansion from other contenents.

The Kahn is another story. I know he'll probably attack me at some point. Right now he is weak and impeaded in expansion by jungle. I could probably take him out with no problem. However, I do not want any of his cities right now. They are stilll fairly far away and I have much better land around me. So, if I take him out, I would be razing all of his cities. While this would make sure that he couldn't cause me any problems later on, it would also leave a lot of land open for quite a while that could be colonized by a more powerful civ for anotehr contenent. (I'm am way ahead of the Kahn right now and I doubt that he could ever catch up, but if he is anything like Monty, that wouldn't stop him from spaming units at me at some point.)

So, do I raze his cities and take him out or let him keep the land for me until I have enough commerce to support cities that far away?

I would let him build up his cities, clear the jungle, and get a good base for his empire before going after him. This may seem odd since this would allow a rival to rise, but it's better then getting a bunch of useless and expensive cities just for the point of having them.

Later after Khan has built up an appropriate nation, go into a protracted war to stop his expansion and economy for a while and greatly weaken his military, and then invade him. By then the cities won't be worth razing.