Here's a comparison of how a single type of bulb (Phoenix 250W SE 10K) does on various ballasts:

http://www.reeflightinginfo.arvixe.c...&Submit=Search

Note that the electronic ballasts use pretty much their "as advertised" wattage (power column). Compare this to the increased power usage of the magnetic/TAR and HQI ballasts, but at the same time you get more useable light (PPFD column). Note also how colour (CCT column) varies according to which ballast the lamp is on even amongst the three electronic ballasts.

The same concept holds true for T5s. An Icecap 660 ballast will overdrive a 54W T5HO lamp to about 80W and an increased amount of light will be realized, but at the expense of somewhat shortened bulb life if you don't employ proper cooling. In contrast a Workhorse ballast won't overdrive, but you'll end up with less light.

However, this lowered bulb life expectancy does not occur with HQI/TAR ballasts in MH as you might expect IME.

In the end, you must choose your bulb/ballast/reflector combination carefully according to your own needs and tastes. I suggest that you look at as many other tanks as possible before settling on a particular system. It's usually a trade-off between looks and growth.

You certainly get more PPFD out of an HQI ballast but that doesn't always hold true for standard magnetic, especially with 10k bulbs.

PPFD varies considerably as well in some cases.