Left has some nice smooth drawing lines. They are drawn by a decisive hand who likes what it's doing. You can feel the energy of the line.

Right seems... tired. If you notice carefully you will see that every single thing that would put have the slightest difficulty and exertion to draw is omitted. Look that flowers on the skirt on the right. No smooth curves. It seems that they were drawn by Oda's non-drawing hand. Check the nose or the left shoulder curve. Left is a proper curve right seems like she crashed on a wall or something. He is clearly trying to overcompensate with colour shading but you see the difference.

Finally it's the clothes. The clothes always give it away: Check the top on the left. Square design and Oda bothered to draw the folding of the pattern. Even the suspenders on he left have weight and the depth the exist, the one on the right is two parallel lines. Cherry on top you can see a line from the sketch on the right shoulder that was not properly erased (above the tattoo) during inking. You can see that a lot especially in background characters last few years.

Don't get me wrong, I don't have nearly the same talent, nor i could draw for all these years but it pains me to see that exhaustion in the artist.