Consider this... Krav Maga was constructed specifically as a self-defense system. There is no sporting aspect whatever.
Muay Thai is a sport. It's conducted in a ring, with gloves, with rules, a referee, and an opponent who will be using the same style and who is approximately at your size and skill level.
Can you say this about a self-defense situation?
Muay Thai has no grappling component, and no defense against or use of weapons.
Muay Thai
There is no "better" martial art, only a martial art that is better for you.
Krav Maga. It's for murdering, whereas Muay Thai is for self defense and sounds like a floaty bar drink.
Muay thai or krav maga