Changing from CFL to LED on the last 4 weeks of flowering

I just finally got the money together to order my new 1200 watt LED grow/bloom light. It will be here in about a week, the title says it all.

But will it actually benefit from the bunches of new light or will it just grow as if it was still dealing with cfls seeing as half of the bud production has already happened?
Should I just wait this grow out and start fresh with the light next grow?

Thoughts and opinions please!

not gonna be true 1200 watts but should be better than the cfl's

Use both.