Would it be more effective to terraform other planets or to modify our own physiology?

It seem to me that if/when we get to the point of colonizing other planets, attempting to change their surfaces and atmospheres to match ours would be immensely expensive, complicated, and difficult. In contrast, it seems as though it would be much easier to, say, genetically modify ourselves to live in low or high gravity.

Note that I have only a limited grasp of the (largely theoretical) technologies involved, so my thoughts are based largely on intuition.