i prefer both, because in this way you can earn more and you well know the matters outside from bitcoin. bitcoin just need your small part of attention, this attention contain focus and strategy.
You are right we can do bitcoin together with our main job, we can arrange time after work or on week end, maybe by the time we are retire from our main job we can take full time to fill time with positive things .
Because bitcoin can still be done in our spare time every day and we are still can working on bitcoin at leisure time, so we will earn revenue doubled in weekends or months. Having two jobs is the best way to earn a better income for future purpose.