Having been in your shoes more than once, here is my cost benefit analysis.
The dealers get the kind of jobs that no one wants or can do plus warranty work. It used to stay pretty interesting. In the seventies a shop wrench had to do what ever came along, general tear down and assembly, rebuilding components, welding and fabrication, pre-delivery and general troubleshooting. Now days each of those areas go to certain people who have been pigeon holed. That involves politics and whether or not the shop foreman feels threatened by you. Like it or not you will be pigeon holed eventually and the types of jobs assigned will fall into a single category. The other part of working in a shop that I had the biggest problem with was concrete floors. My feet ended up killing me after a couple of months to the point of losing sleep at night. Most of the shop foremen are good people and they are only going by human nature. The people who can do the tough projects always get them. Those that can't end up with the gravy, because that is all they can do. And when they lose money on a job, their time is shifted internally to any job that is making money. Basically those that are good end up carrying the dead weight. It might not matter to you at first. It will grate on you over time like a burrowing insect getting under your skin.
The field is where the best wrenches really shine. To me, that is the top of the profession. You not only can handle yourself with the wrenches, but you also have learned about company policy and how to apply it to customers, how to handle customers, understand billing processes, usually you are the safety officer on a project, you are also a project manager and so on so forth. It is a job with a ton of responsibility and commitment. What goes with that are huge demands on your time and it takes a lot away from your family. The territory the dealership covers will give you a hint on how much time you will be away from home. Get a map and make points on it showing the limits of the territory you will be expected to work in. Figure the miles from your base to each point in the square and then look at the types of customers at those points. You can just about figure that a drive of more than and hour and a half is going to entail a night or two in a motel. Four or five big companies with lots of your equipment more than an hours drive away might mean you are sleeping with bed bugs for more than a week a month. Last field truck i was in for a dealer put me on the road at least two weeks a month. The doesn't count the trips out of state that got thrown on top of the truck time.
One last thing, the money in the field is great but a lot of it gets eaten up in taxes. You have to plan for it.
