It sounds like the refrigerator has a slight vacuum in it. I'll bet the right door holds the left door flap sealed. So it's harder to open the left door because the seal and pressure from the right door keeps the vacuum strong longer than the right door. But the right door has no flap and therefore a smaller sealing surface making it easy to open. Then once the right door is open there is no vacuum so the left one is easy to open.
A test to prove or disprove my theory. Find something small like maybe a matchbook that you can temporarily close in the right side door to hold a portion of the gasket away from the refrigerator and prevent it from from sealing. It doesn't have to be much; Just something to hold the right side door gasket away from the refrigerator cabinet. Now with no vacuum see if the left door opens any easier.
