In Any Case B is Taller!

Why the height comparison?

 B will be always taller in any case.

Case 1 : If A and B are standing in the same row the obviously B is taller than A as B is tallest among all in that row.

Case 2 : If A and B are standing in the same column then still B is taller than A as A is shortest among all in that column.

Case 3 : If A and B are standing in different row and column then there must be somebody C which has same column as A and same row as B. This C is shorter than B (as B is tallest in row) and he is taller than A (as A is shortest in that column). That is B > C and C > A.

Hence, in any case, B is always taller than A.