Mag ballasts are less efficient, and can buzz.
Electronic ballasts can be very efficient, but often create a lot of electronic noise and blank out radio reception. They may trip GFIs.
Also, they are generally made in china, where the UL or CSA recognition may be obtained by payment of bribes, not actual compliance with rules..... They MAY be safe, and MAY meet the radio interference rules. But then, they may NOT, and may just fail and burst into flame someday......there have been some recalls recently.
Unfortunately, I have knowlege of cases where a product unit failed US testing due to flammability, but passed when "testing" was done in china. The products have been sold internationally, with all the safety marks printed on them....the same marks that the US testing said could not be applied.