250w vs 400w HPS?

I'm keeping freshly planted clones and a few seedlings and even a few young adults under 250 Watts right now to try to slow em down

I'm going to have to bump it up to 400 soon but I don't have any problem with 250 when it will suffice

I would run the two 250's that you have over one 400 just for the spread and adjustability alone ?

Your plants can tell you about their needs. In young plants look for excessively long petioles, you may see that before you see node stretching.