There are long standing debates on what the "Best" bulb is. IMHO, you need to figure out:
What will be my livestock?...ie; SPS, LPS, mixed?
Do I want a white light, or bluer lighing?
Wattage? You need to question what type of ballast u have electronic, etc.
Will you be using supplimental lighting ie; T5s, VHOs, etc.?
Is it Double Ended (D/E) or Single Ended (S/E)?
lots and lots....
....a 14k bulb will be much bluer in appearence than say a 10k bulb, but may not be suitable for a strickly sps tank. I run XM 10k's thy have servd me well, and i have alot of light...wattage is important as well...Do some reaserch here using the search tool and you will see many different ideas
im just really skimming the surface of this decsion...thrs lots to consider..
gl