[BiseCreesia]

Rather than think about the probablity of a goalie saving a penalty (which I think over-complicates things), would it be sufficient to consider the goalie's available radius against the goal size in the two instances to get a sense of the advantage? If so then perhaps it becomes a trivial problem that even I could manage if I could remember any of my maths from all those hundreds of years ago.

Yes. By moving 2 yards forward, he decreases the effective surface area of the goal from 192 sqft to 133 sqft.