When many people think of good jobs, they often think of something that has high social stature that pays well. However, sometimes the best occupations are the ones that are menial and simple. Take a lady I know, for instance. For lots of years, she worked as a chef for busy restaurants and hotel restaurants. But when I met her, she was just working at a small café. The reason was that she was tired of working high stress jobs. She needed a break. So she worked at the café because it was a simple, relatively low stress job. Having a career in a challenging field can be good. But sometimes the best and most enjoyable jobs are the simple ones.
This is a tough one. I remember all the years working stupid hours at the hospital. Hardly a day went by without daydreaming (typically in the canteen whilst eating disgusting hospital lunch with colleagues) how great it would be if instead of being doctors, we were landscape gardeners, florists or writer/singer/insert whatever other hobby people had. This tendency was directly proportional to whether you were doing a week on-call and how much sleep you got lately. Landscape gardening figured prominently because it was working outside in fresh air, sun on your skin, being healthy and relaxed instead of stressed and overworked.
Sometimes you need to have worked the high stress, demanding job to appreciate those that are less exerting and less stressful. I don't think either one is all that fulfilling in the long term. To me, the best job is one that engages you intellectually for long periods of time and one in which you can actually see something being done. That doesn't mean it has no stress. Nothing is going to be perfect all the time. The middle ground is preferable, as those simple jobs can get pretty boring after a while. (Unless you've got some sort of hobby that you devote a lot of time and mental energy to, and you end up in a situation opposite to what most people end up with -- where the time on the job is actually your "down" time.)