Thanks for all the help, gents. We've had some family issues and this project has taken far longer than I'd like.
My shop is a disaster. I'm trying to get it straightened out after a whirlwind house renovation. Hopefully, seeing the condition of my shop will help you folks feel much better about yours. lol!
Anyway, I'm happy enough with how it turned out. The 6" bench behind these cabinets extends the work surfaces but this is where the dust collection pipes will come up to service machines on these cabinets.
If I were doing it again, I would certainly use maple trim. The few dollars I saved is entirely irrelevant. These are intended to be cheap, simple, and disposable. If one gets too natty, I can build another with two pieces of MDF and a few strips of solid wood. Still, hardwood would have made sense here.