I did sloppy math before and agree with polarsi's and others corrections. Long term if you've both got 50/50 then you'll be right 2*(1/2)*(1/2) = 50% of the time. I just left the 2 combos of being right on both ends of the spectrum. I should self ban myself from posting after 10pm, and yet here I am, doing it again. I think my dumb math distracted from original question which was geared around the impact of getting this guess right or wrong.
If you are running against me would you rather be up against:
a) 4-3 def with 3 LB in coverage (0 on the line) and expecting a run
b) 4-3 def with 2 LB in coverage (1 on the line) but expecting a pass
My guess would be that you would rather see option B.