To work ALONG WITH HVAC, I'd go with electrical. You'll use that knowledge much more.
If it was INSTEAD of HVAC, or as a backup career, I'd go with plumbing. Plumbing leads much more to problem solving, and making a distraught customer happy.....which, like HVAC, is a big emotional driver for many.
Comparatively, very little electrical work consists of "saving the day" for someone....unless you're into heavy controls work or something of that nature.
:.02: