"What makes them different?" vs "What is it that makes them different?" Is there any difference between the two questions?

Question

If we want to find out whether there is any difference between two similar things, I heard the following ways of asking about it (the first being more common):

"What makes them different"?

"What is it that makes them different?"

At first, both questions seemed same in meaning and but when compared, I think there is a small difference between the two questions.

Although, both questions ask the same thing(s, the second one assumes there is probably 1 thing that is different. And the first question does not care about how many differences there may be in number.

This is what I think, however because English is not my native language, I can't be quite sure.

Am I right in my thinking?

Answer 1

Firstly, if you want to know about the difference between the two, I suggest adding 'from each other', as the way you phrased it could also mean 'what sets these things apart from other things?'

As for the difference between the two, you're right: the second option ("what is it that makes them different [from each other]") places emphasis on a single, or the single most important, difference.
But it also asks for a cause of the differences more than your first sentence ("what makes them different") does.

The intended interpretation of your sentences could ultimately be gleaned from the eventual context, though.