It’s just physics, but in theory the 28c will have less grip and you’ll have to run these at slightly higher pressure so also slightly less comfortable. But the difference will be very small, and maybe not even noticeable. Also, if you switch manufacturers there might not even be a physical difference as they all seem to have different ideas about what size means. I have 28c Continentals on one bike and they measure 30.6mm at the widest and I hade some 32c Vittorias (exact same rim) on another bike and these measure 30.2mm at the widest. Go figure.
Not an answer to your question, but most cyclists (me included) have ‘gear acquisition syndrome’ really bad. One of the symptoms is getting an idea in your head that if I just bought a new thingabob for my bike my riding would be sooooo much better, but that’s generally not the case and it’s better to ride what you have into the ground until it’s time to replace it.