Quantum.. if your picking between those two. There are plenty of other ballasts that are equally if not better for less, but off hand I can't remember. I have buddies used Quantums for years never an issue, and have buddies on Lumateks and have had them in for repair, replaced etc.. I mean "any"
manufacturer is going to have issues, I think its just a matter if the buyer is some what lucky or not. All ballasts run hot, period.
I mean I have bought top of the line for years because I could, money wasn't an issue, I was buying the name nothing more expect maybe some exaggerated claims or at beast really getting minimal gains. I mean sometimes you can buy 2 ballasts for one "Bad Ass" "Lumatek" "HydroFarms" etc.. you know what. They are pretty all made in china by the same factories and people, just names warrant price and somewhat fabricate lies.
I like real world people telling me what to expect, and I research plenty myself but now I leave the "hearsay" or "unverified real world claims" these commonalities are making. I mean what better market to fool, manipulate and control then some stoned pot heads? No offense to anyone, but come on any one with common sense after a year of reading, watching and asking questions that 95% info, claims and trends are fabricated for one thing. Dollars. Not bigger buds, more lumens, special spectrums etc.. dollars.