TLDR at the bottom
I'm fortunate enough to have some options at my current union job. There is a system where a worker can bid into another department, try it out for 60 days (90 with an extension), and either keep the new job or go back to their previous position. The only penalty for winning a bid is the loss of bid rights for 2 years, regardless if you stay at the new job or go back to your old job.
While considering these jobs, I am trying to look at what position I'd likely be in after a few years, and where I'd potentially be should I stay in that department until retirement (probably have another 25-30 years until then). Keep in mind wages usually go up a few % each year/new contract.
Job A:
My old job. It is a good job that causes little stress. There is just a small amount of physical labor, mostly doing quick fixes to equipment jams along an assembly line. The other apsect is picking up product off the end of the line with a clamp truck (fork lift type vehicle) and loading it into rail cars.
Within 2 years I know enough people will retire here that I'd move into the 2nd (middle) position on the line of progression. Here is where I'd likely be stuck for the next 10-15 years. The job itself is very easy. In fact, on an average day, guys doing this job spend most their time playing solitaire or fucking around on their phones. Basically you are a equipment babysitter, who makes adjustments to how the machine runs. Total cakewalk job. Pays $25.50/hr.
Job B:
The first line of progression I trained at in the new department. The bottom jobs here pay more (starting around $26.50/hr) than the 2nd job in my old department. This job involves covering a large area, indoors/outdoors, and making sure the complex conveyor belt system continues to run properly. If you cannot quickly fix something, there are trained millwrights you can call to do serious mechanical work. Every day you get dirty (covered with sawdust and slight odor from some of the equipment's chemical processes) as there is much cleanup every day. However, you are usually not doing serious work all day long. The main labor is just walking up stairs and to various locations. One could likely walk 10+ miles in a shift. I don't mind this.
On a bad day, you could be shoveling or swinging a sledge hammer for 12-16 hrs. "Bad days" normally happen once the temperature drops below 18 degrees F. That is the magical number for outside equipment to start having issues.
In 10 years I'd probably have a less physically demanding job in the department that pays $29/hr. However, due to the number of people who took this line of progression, I'd probably be 20 years or more away from an operator position (top job).
Job C:
The other line of progression in the new department. The earlier jobs here mainly involve working in a chemical plant, doing tests, and running errands for the operators when they call on the radio. About half the work involves collecting chemical samples, testing them, and reporting the data to the operators. I have to shave for this job because I am required to wear a gas mask in certain areas. The building has lots of stairs to access equipment, but not as much walking as job B. We also hook up chemical rail cars to pump their contents throughout the mill.
There are horrible chemicals and gasses used in this area, as well as an extremely high voltage electrical system that is used to cause a chemical reaction/process. If you notice something drip on you, DON'T LOOK UP. Walk out of the area and then try and see what it was. For the most part you can just wash things off. However caustics have given people chemical burns in this area.
There have been occasional equiment/operator/management failures that caused property damage. There is the potential, however unlikely, to be in the wrong place at the wrong time and have a large tank burst/explode. The result of this would likely be fatal. Either you would be blown up, drowned in caustic chemicals, electrocuted, or a combination of all 3. With that said, it is pretty well known when equiment is trending toward a major failure. This kind of shit is highly regulated.
This department works the most overtime. At the end of your 12 hr shift, you could be forced to stay another 4 hours, go home for 8 hours, and have to come back for another 12-16 hours again. Your "weekend" could be approaching, and in the last 10 minutes of your "Friday" (in quotes because all the shift work is a rotational schedule where weekends could be in the middle of the week), this could be forced on you.
The work is much more mentally demanding, but not so much physical. Most people are intimidated by the "what ifs" from this line of progression and choose the other one. Within a year I'd be making around $29/hr. I'd likely be at the top (and higher paying) job well before retirement.
In addition, Jobs B and C have their busy seasons on the one month I normally take a vacation or two. There is an activity my wife and I enjoy that can only be done in September. I might not be able to do it every year, or hardly at all, if I work B or C. At Job A, I have no problems scheduling vacation whenever I want.
TLDR: What would you prefer?
Job A: $25.50/hr least overtime. Very little actual work. Low/no stress. Can get vacation when I want it.
Job B: $26.50/hr more overtime. Some dirty work, potential physically hard days. Hard to get vacation when i want it.
Job C: $29.00/hr more/most overtime. A lot more mental/situational awareness required. Many hazards. Hard to get vacation.