Man I love when this thread reappears, it usually gets so lively. That aside, if the local union has a good service training program, and not all do, by all means go for it. In the long run you will benefit. Going the same route as non union is a hard row to hoe unless you're lucky enough to find one of the few companies that is dedicated to their employee's education. Granted, it can be done and if you stick with it and push yourself to learn more and try to be the best you can be you can make more money than union counterparts and if you're smart enough to only work for upright companies you can get a better benefit package than the unions offer. Beware, working union does not gaurantee you a job or an easy one at that. I manage a union shop and my guys are out there working overtime to get a building back up, or running emergency calls nights and weekends when the temperature drops to -20. This is the service trade. Our local can no longer provide us with trained commercial technicians and last ones they sent over we fired. Go into this with your eyes and mind open, good luck.
Don't let your ego get in the way of a good decision