"is there any difference between ..." or "are there any differences between ...", which one sound more natural? I searched both in Google Books and both have a lot of results.
We use a singular form when we mean or expect one difference. This could be a difference of nature.
Is there a/any difference between these balls?
One is red and the other blue
One is wooden and the other made of rubber
Is there a/any difference between these two ropes?
One is thicker than the other.
One is made of nylon, and the other is made of natural fibre.
We use a plural form when we expect that there are (or may be) multiple differences.
Are there any differences between these pictures?
One has more people, fewer cars, and a cloudier sky than the other.
Are there any differences between these models of the same car?
One has air conditioning, a radio, and heated seats. The other does not, and is cheaper.