120v runs double the amps of 240v, both use same wattage. So if you run 120v on a normal 120v 15 amp breaker with normal 12-14 gauge house wire your pushing roughly 9 amps, so can only run one. Where as if your running on 240v your using 4.5 amps so can run more lights per breaker but at 240v need to use double breaker and might as well use double 30 amp breaker with 10 gauge wire, then can run 4 lights safely on a light controller.
So if your planning on only running one DE and no plans of ever using two just get the 120v plug option. Just don't run anything else on that breaker except something under 3 amps like a fan.