What's more important? To be good at logic or to know your percentages? I'd say, the former—by far.
Sure, it is nice to know that a finesse is 50-50 – but who doesn't know that? If you are in an 8-card fit, they rate to break 3-2. A 4-1 break is less likely. There are a few basic percentage situations that most of you know in your sleep. How about this one:
A J 10