Are "Grow" HPS bulbs that much better?

Hi-ho,
Shopping around, I find a typical 400w HPS bulb has about 32k lumens in 21Kelv. for about $25.
The "grow light" versions seem to have maybe 10% more output. They have a little broader spectrum, but still peak at the same wavelength. They cost around $75.

Has anybody done a grow comparison?

Advanced thanks for sharing the wisdom!

A bulb for 300% the dinero for a 10% increase in lumens (320). RIP OFF! If you want an increase in lumens get a higher wattage system.

Waste of money IMO. If you want broader spectrum and higher lumens add a metal halide and more watts.

Sorry but I try to tell everyone that has yet to buy a bulb,,
to check out Ceramic Metal Halide (google it)

There is a post in advanced forum and there are a few grows here using it

While not particularly great for a large commercial grow it is the bomb for personal medical grow, if that's what your into you'll thank me