More and more future doctors consider "work/life balance" as one of the major determinants when picking a specialty. The fallacy regarding work/life balance is that all time spent at work is spent working and all time spent at home is spent leisurely or with personal activities. These assumptions are not true.
Let's consider the following example. I like emergency medicine and internal medicine. I've heard that in the ER, I will work 5 shifts of 8 hour days per week. In internal medicine, I would work 10 hours a day for 5 days per week (This is intentionally a very crude example).
ER: 5 x 8 = 40 hours/week
IM: 5 x 10 = 50 hours/week
That's 10 extra hours per week -- 20%!
What the above calculation doesn't take into account is the idea of down time and how productive a clever person can be with it. In the ER, I would be running back and forth between patient rooms and constantly checking for lab or image results to discharge. I hardly have time to catch lunch. In IM, as long as I finish all my work (which I can often do in just 2-4 hours), the rest of my time is open.
So, what are the implications of this? Let's say I need to read a paper that my attending handed me. This will take 30 minutes. In IM, I can do it at work which saves me 30 minutes at home. In EM, I will likely have to do at home which burns 30 minutes at home. In this example, we have a net gain of 30 minutes of home time.
Even more striking is the difference when you consider doing home tasks at work. For example, browsing for fellowships or even ordering groceries online. Your gains are both saving home time AND eating away at work time. So, a 15-minute online grocery excursion actually offers a net gain of 30 minutes of "home time" because work time becomes home time!
These small time gains add up quite quickly as you can imagine. Suddenly the difference between specialties swings dramatically when it comes to time consumption. While this is obviously not the only criteria for picking a specialty, it's definitely food for thought.