2-man Mechanics

Our mechanics class teaches 3b extended and explains that it is easier to see the tag / no tag if it is a sweep tag (throw up the 1 b line, runner slides with hand extended to plate).  You also have the play in front of you, you can see when the catcher catches the ball (at which time he can block the plate) or if he blocks the plate before the catch (obstruction).  Also you are "out of the way" if the throw is off line up 3b line wide.

As a generalization, 3BX is better for swipe tags; 1BX is better for collision tags.

Since there are so few (legal) collision plays, 3BX is better than 1BX.

And either way, you still need to read the play and adjust.