A nice person will behave according to the norms and might comfort you but will literally contribute zero to your overall well-being.
A kind person will behave genuinely to improve your well-being even if it makes the interaction uncomfortable for the moment.
You're trying a new dress and you seem you liked it and are checking the opinion of the other person before buying. A nice person will confirm that you should buy it by seeing your happiness even if it's obvious that that dress isn't a good fit for various reasons. A kind person will be direct and sharp to express that it's not a fit but also will provide the reasoning and will definitely help you to find a better one.
Are you a kind person or a nice person? Do you prefer having kind or nice people around?
Which one is better?
Irrespective of whatever you take, do your inspection because it will reveal a lot about yourself.
My take is that have you ever cared how apples get rotten?