opinions vary......
depends on what Kelvin you are looking for.
alot of people, including myself, use the 14K Phoenix for the "bluer" look buy with higher on average PAR than most 14K bulbs. Had the Ushio 14K and some like Hamiltons......
It really depends on what you value more, the "look" of the tank or the "performance" or growth rate that one has.
as a rule that most use: (this is a general guidline in which all bulbs do not fit into this model, but helps in understanding the major differences and classification)
10K=yellow in color and have the most PAR which equals faster growth.
on the other end of the spectrum
20K=blue in color and have the least PAR which equals slower growth.
Obviously, bulbs in the 11K-19K range are a combination of the two bulbs, which is why 14K tends to be a popular choice.....best of both worlds......
The key is finding the "look" you like with the highest PAR for greatest growth rates. Which is why you see people always playing musical bulbs.....which I myself am guilty of
Unfortunatly, MH bulbs are slightly different in "look" and "performance" bulb to bulb, manufacturer to manufacturer even in the same rated "K" rating.
Combine this with different wattages, ballast options, supplentation options (none, VHO, PC, T5s), the options and color and power combinations are literaly infinite.
In the end its all very personaly subjective and I can only recommend pick what you like to look at and concentrate on water quality and stability to maximize growth because they can contribute to high growth rates just as much as light. Try looking at other tanks with simmilar lighting combination in person.
You will probably have a bunch of spare/old bulbs as you figure out what you like......which I think is what you need to do to dial it in.
I would try to stick with name brand bulbs and refer to Sanjay Joshi's site for further articles and spectural analysis of bulbs and ballasts......
Trial and error is what eventually happens with all, considering all of this and all of the other variable parameters that differ from tank to tank that effect color, and growth.......does anybody really know?