Could and may show that a speaker is 50% or less certain about a present situation. So, both sentence, a speaker don't think as the other one think. It's 50% shared.
I agree with MSoni, but a bit different. Could is used to show the possibility(no opinion from the speaker) May is used to suggest something that is possible (in the speaker's opinion)
Yes, meaning is very much the same . A little difference ,as I feel, may be: Could= just possible(speaker is not talking about chances of happening) May =likely to happen
In certain contexts there could be a difference. My personal feeling is that in that sentence 'may' could (!) express a greater likelihood of there being a difference.
However, it is not possible to state categorically that there is a difference or, if there is a difference, how great that difference is. We certainly cannot say for certain whether the speaker intends, or the person