What a jalapeño has that a habanero lacks
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
tilde
(Other definitions for tilde that I've seen before include "Augmentation of text" , "Accent on some Spanish words" , "Mark over the letter 'n' in Spanish" , "Significant mark" , "Accent (used over n) in Spanish and Portuguese" .)