you will probably get nuissance tripping with both those lights on the same 20 amp circuit. Any kind of current over like 16 (80% rated) amps is getting sketchy. If your electrical system is working properly it is just annoying and not really dangerous.
Any chance of putting them on seperate circuits? could just be an average 15amp, and then you still got a few amps to work with for other goodies. 12 amps max for 15amp circuit.
the electronic ballast will probably draw less than the magnetic, but not much, 1000 watts is 1000 watts , mathematically it is 8.3 amps (at 120v) but that is at 100% efficiency, plus I believe those ballasts will spike at startup.