On the left picture its the far right on the middle row which has to be switched with the middle box in the bottom row in the right picture. (f and 8)
or
On the left picture its the middle box in the bottom row which has to be switched with the far right box on the middle row in the right picture. (h and 6)
because
The boxes have to be the same from top right to bottom left

but if you want to get just ONE answer
I'll go with the blue circled one
because
Then there are always exactly two rows with rectangles in each of the boxes. Otherwise it would be "more" odd if on side had 3 rows with boxes including rectangles and the other just 1 row.