"What's the difference between..."

I was wondering if there' s a simple pattern for asking the difference between two things.

For instance, I was staring at two trays of 花生糖 (peanut candy) at a street-vendor's and wanted to ask what's the difference between the two before choosing. (I managed to get this across with pointing and mumbling something, but, not so elegant).

So, how do you say, "What's the difference between these two (peanut candies)?"

Any other related phrases would be much appreciated too!