When describing the way people look, both words indicate neatness and elegance, but sharp is better suited for someone who's also stylish and fashionable. Is my understanding correct?
sharp vs smart
sharp can also mean quick-witted. someone who can do multiplication in their head easily could be described as "sharp." looking sharp also means well dressed, like being smartly dressed.
When it comes to appearance, 'sharp' means that someone is dressed in such a way as to attract attention in a positive way.
To look or be dressed 'smart(ly)' is to use a somewhat older term, and therefore wontedly carries the connotation of being a a little less modern (as older folks are not up on the latest fashions)--still neatly dressed, but a little on the frumpy/nerdy side...like Orville Redenbacher (at least here in the US it does). If an older person is saying it, it means 'sharp', as 'smart' was the way they said 'sharp' back in the day. Again, it's rather antiquated terminology.
To look or be dressed 'smart(ly)' is to use a somewhat older term, and therefore wontedly carries the connotation of being a a little less modern (as older folks are not up on the latest fashions)--still neatly dressed, but a little on the frumpy/nerdy side...like Orville Redenbacher (at least here in the US it does). If an older person is saying it, it means 'sharp', as 'smart' was the way they said 'sharp' back in the day. Again, it's rather antiquated terminology.