It's probably mostly idiomatic. For native English-speakers it is more natural to use "number" when talking about things that are counted units that would be represented by integers (like marbles, or children, or features). "Amount" would be more appropriate when talking about something that you measure and represent with a floating point number (like butter, or gasoline/petrol, or risk). But an English-speaker will understand what you mean if you say "amount of features" instead of "number of features."
And since we're being picky, it should be "the latter is correct", not "the later is correct."
And since we're being picky, it should be "the latter is correct", not "the later is correct."