MDF baseboard is more resistant to dings than plastic varieties and some soft woods like pine and poplar.(Yes, I am aware polpar is classified as a hardwood, but classification has little to do with actual strength of the wood)

However, making a scarf joint---the angles cut used to join longitudinal pieces of trim are very difficult to make with NDF as the sharp edges of the scarf joint break off easily and making a coped joint for inside corners has the same problem.

If you can solve or work with those gotchas, and you prime and paint the trim(Not just paint), you should have a nice looking job.

"MDF baseboard is more resistant to dings than plastic varieties and some soft woods like pine and poplar."

Really?

MDF dings and chips much worse than either poplar and pine in the installations I see.
If you have all inside corners you can probably get away with MDF.
If you have any outside corners it is very weak and chips out.
Even a vacuum cleaner hitting the corner can cause damage.
If you want nice molding go to a real lumber yard.
The big box places get there from second rate companies that start with 1x lumber that is down to 3/4 inch.
The baseboard is thus 5/8 thick instead of 3/4.

You are correct about the outside corners.

I referred to the linear sections---and the paper type MDF---not the pressed sawdust that is sometimes sold as MDF.