"It depends" hehe.

There are digital ballasts that can fire either bulb.
There are also switchable standard ballasts depending on which bulb type you have.
There are also conversion bulbs.
And some people bypass the igniter as a DIY project..

I went digital because it runs smoother power, silent, extends bulb life, fires either bulb, has built in protection in case theres a power outage, runs cool to the touch.
Worth the money to me for all that.
MisterE Reviewed by MisterE on . Metal Halide or HPS? I'm looking to buy a 400 watt MH or HPS what's better for growing? Veg+Flowering? Rating: 5