A matter of degree — with one line in it that is a difference in kind: the kittenfisher is a real person, the catfisher an invented one. Kittenfishing is polished-but-real — a genuine person made to look their best-and-then-some. Catfishing is wholly fabricated — a fake identity, often with stolen photos, that doesn't correspond to a real available person.
Side by side
Aspect
Kittenfishing
Catfishing
The person
Real
Fabricated
The photos
Theirs, flattering/old
Often someone else's
Shows up IRL?
Yes
Avoids it
Severity
Mild embellishment
Full deception
What each one means
Kittenfishing
Kittenfishing is presenting a mildly exaggerated, overly flattering version of your real self on a dating profile — old or heavily edited photos, an inflated job title, a couple of added inches of height — without inventing a fully fake identity.
Catfishing is creating a fake online persona to deceive someone — most often into a relationship, but also for money, harassment, or simple experiment. The person you're talking to doesn't exist as described, and the photographs usually belong to a real stranger who never consented.