I obviously have to admit to bias, and also I haven't seen Mitchell play much. Plum was very, very good in the lane though, no problems at all finishing around the rim. She's got all the angles, spin shots, dipsy dos, knows just how to put the ball beyond the reach of a taller defender. And finishes well through contact because she's strong. Both are good at drawing fouls.
As far as my statement about Mitchell not being able to replicate Plum's Sr. year, mostly what I'm referring to is offensive efficiency and consistency every single game, all season long. Plum was phenomenal last year, she didn't really have a bad game all season. If you didn't get a chance to watch her on a regular basis, you missed something remarkable. Also Plum increased her FG% almost .100 from her previous best. That's a fairly stunning improvement, especially for a perimeter oriented player. I would be very surprised if Mitchell showed a similar level of improvement this late into her career.