What kind of fruit还是What kind of fruits

What kind of fruit do you like to eat best?
= which is your favourite fruit?
I like citric fruit best: oranges, lemons, grapefruits...
I like apples, all sorts: green (ones), red (ones), yellow (ones)...
What kinds of fruit are there in the market?
= what fruit is available in the market at the moment?
= of many kinds of fruit which are currently available?