HPS Question - Diffused or Clear(transparent) bulbs?

I'm picking up some 400w HPS lights this week and have an option for diffused or transparent/clear bulbs and I'm wondering what the difference is and which one is better suited for flowering plants?

thanks.

Clear.

Diffused looses a lot of lumens due to the phosphor coating used to do the diffusing. They're more for general lighting tasks in buildings and so forth.

thats what i was curious about the advert said that it was diffused for light but i misread the translation thanks