They are the same. However, adding "do" just emphasizes your point. That's it.

Normally, you say "I like". This should be your first choice for making sentences. Yet as Yusuf has pointed out, you (do) add "do" for emphasis. The times you need this emphasis include: - to clarify a point, especially if a previous statement of yours suggests otherwise. eg. "I don't have a garden, but I do grow my own herbs in pots." You can also add "do" to correct another speaker's wrong assumption. - to mean "really", "very much" or "in fact". eg. "I do understand what you mean, and I do sympathise."