I find ghosting to be more hurtful and most rude. I hate it when people ghost. When you've spent time and energy talking to someone, it's like the biggest slap in the face.

Honesty can hurt, but it doesn't have to -- you can let the other person down in a softer, gentler way. Like: "you seem really nice and I'm sure you're great, but I just don't think we're the best match. I wish you all the best though in your search for the perfect match!"

To flat out just write "thanks, I'm not interested" is more hurtful and a slap in the face. It's all the way it is written. If it is said and written with kindness, the other person will take it far better.