overlap by however many frames you want the transition to be.
When you do it the A/B way...how do you count the number of frames you are overlapping?
(eg you want a 48 frame cross dissolve...how do you mark and count 24 frameseach side in a quick and efficient manner)
Beauty of a single track transition is you can see the cut with and without the transition.
In A/B transitions...you have to appy the transition otherwise it looks like the cut is in the wrong place (early)