Decisions, decisions...
I have, and run both. Ups and downs to both... Yes, the digitals do run cooler, more efficient and put out more lumens- all by small margins, however- especially considering the price difference. On the downside, if you blow a digi ballast, you get to wait for it to go back to the manufacturer, where if you break a mag. ballast, a good hydro store generally has the parts in stock to fix it that same day. Cheap. Also, no issues with magnetic ballasts on flip box setups, since there's no 'error sensing' technology to screw things up.
Magnetic ballasts are an old school, tried n true tech- and most bulbs out there are designed to work with them as opposed to digitals. You need to pay careful attention to the brand, quality and price of digital ballasts, as they are most emphatically NOT all the same. For example, I keep hearing bad things about Lumatek, though mine is currently running fine.
I would consider starting with magnetic ballast tech, then once everything is dialed in on your grow and you've mastered the basics, consider the upgrade for the uptick in efficiency. That way, you get to learn with cheaper gear- and when you upgrade you'll still want to keep the old lump around as a backup 'just in case.'
Spend the extra few bux and get the 1000W magnetic ballast that can be switched between MH and HPS, and from 120V to 240V. This way, it's a backup or a switchout for any situation you'll encounter.
Not true re. the 600W on a digital ballast being equivalent to a 1000W on magnetic. The efficiency differences are on the order of 10% or less. The mag. ballast is a chevy- it may not be as fast as a Porsche, but it's not as finicky and it sure beats walkin'!