the phantom is supposed to be the better ballast from what i've read.. i've heard a lot of bad stuffs about the lumetek digitals, and i wouldn't get one for that reason.. i had originally gotten the phantom, but had to return it for some reason i don't remember at the time.. i ended up getting the galaxy 400 watter, and love it thus far..
as far as bulbs go, i'm a believer in getting the better bulbs.. i tend to run the eye horilux with added blue spectrum and i also just picked up my first digilux bulb as well...
there was a thread on here before where dude did a side by side with i think it was the eye bulbs, and a cheaper brand one, and the difference's were enough for me to want to spend the extra couple of bucks for the better bulb..
it's really up to you though.. get the cheaper one now if you want, and see if you're happy with it, you can always go ahead and get a better bulb down the line if you're not happy with the one you have now, no harm no foul...
where the more expensive bulbs come into their own is in the lumen outputs, and also sometimes they have a much broader spectrum that is better suited for growing with, instead of just lighting up say a dark parking lot or what have you.. most bulb manufacturers will have a lumen chart, as well as a spectrum chart.. compare the two, and i'll bet the more pricey bulb will beat the cheaper ones in both dpts..