I would say it depends on the rates of the other company offering the free gift card. Is what they are offering just promotional and then you get hit with the real rates? You know, kind of like the cable deals where you get cable for $20 bucks a month for a year and then afterwards you get charged regular rates? I see these companies doing all kinds of gift cards and giveaways and it's just apart of their marketing and advertising. If the company I have is cheaper than there is no need to change just to get a gift card.
The quality of the service matters more than the perks and freebies being offered. I would rather stay with an old yet trusted utility provider than a generous one with a shady reputation. Perhaps the gift cards are just part of a diversion tactic. There are real issues at stake such as overcharging or poor customer service, so they're probably giving away gift cards to mask these problems. I'd rather stick with the provider I trust.
If I am very satisfied with my current electricity company then I am unlikely to switch over to another provider simply because there is the promise of gift cards. What if that other provider is not meeting up to good services on the long run, that would turn a regrettable decision that was taken.