600watt MH/HPS Question

I'm ordering a 600watt digital ballast from HTG Supply. I am not sure what brand of bulbs to get. I am on a tight budget so I would prefer buying GrowBright brand bulbs instead of the more expensive AgroMax brand bulbs. What is the difference in quality between these bulb brands? Is it worth spending more for the AgroMax?

Thanks in advance.

I've ordered a lamp from HTG twice now and always got a bulb included.
If you know your not getting a free bulb just go to Lowes or Home Depot and buy a bulb. It might not be perfect color spectrum etc. but its what I use when I replace my bulbs and I grow the killinest kill you ever seen with 'em.