Our plastic electric kettle is warped from heat and we're looking for a replacement that promises to be more durable. Should we stick with an electric kettle (more efficient?) or switch to a old-fashioned teakettle to boil over a gas flame on the stove? And which, we wonder, is more efficient? To be frank, we're not sure how to answer this last question—our physics is a bit rusty—so we thought we'd ask the audience.