NLAW is a very basic ATGM. Short range, simple optics, single stage warhead. It's lightweight and cheap and simple to use, but you have to be very close to the target.
Javelin is a longer range weapon with excellent optics and it has a tandem warhead to take out ERA. The CLU is good for spotting and rangefinding even when you're out of missiles. Javelin obviously a lot more expensive than NLAW, you can probably get 10 NLAW's for every Javelin.
Horses for courses, I like that Stugna-P for it's remote firing capability. Both the Javelin and Stugna have better optics and longer effective ranges than the tanks they are shooting at.
The AFU has demonstrated that all 3 are effective against the T-72/80/90 family- we don't see very many pictures of destroyed Russian tanks with their turrets attached.