I would say that just go with what interests you more. If you end up deep sea, there are going to be long days, so you better be interested in what you do. Engineering has always appealed to me more than deck operations. This isn’t to say that I am not interested in seamanship, it is just that I am more interested in engineering. Now, since you state that you are older, I don’t know which academy that you are interested in.
I don’t know how other academies do it, but I do know that when I went through KP, one made a preliminary choice of deck or engine. If you chose engine (like I did), my first quarter classes were geared toward nautical science (basic navigation, piloting, seamanship, knots, splicing deck operations, etc.). Conversely, those that chose deck initially, their track on that first quarter was geared toward marine engineering. During the second quarter, the tracks were reversed with the potential engineers taking marine engineering courses and mates taking nautical science. It was only after those first two quarters that the student then made their permanent choice.
I would say that there is probably more physical labor in engineering. I like it because there is more problem solving, trouble shooting and solution creation. This isn’t to say that I didn’t have some really rotten days when I was sailing, because I certainly did; but that will happen in any position and any job. I can say that of all the work I have done in my nearly 40 years of being in the work force, I had far more job satisfaction when I was sailing as an engineer than anything else. Pay was important, but really secondary to be honest. When I worked on ocean tugs, my pay was more than the captain, just because of the way the overtime was structured. But that really didn’t matter.
As far as day to day operations, you will get time to see the sun and seas. Most modern diesel ships, should you go deep sea, run unmanned engine rooms at night, so the engineers do their maintenance during the day, with one then designated to respond to alarms overnight. For those with watches, just like on deck. the day is broken down into six four hour segments, and watches are stood twice a day for four hours.
As far as going ashore, it all depends on your work load, assignment, etc. I found that I had just as much shore time as anyone else on any vessel to be honest. As with anything else, if you do what you enjoy, it will be a lot less like work. When I went to sea, I didn’t have a hobby. My work was my hobby.