You're in luck Bob: I just happened to have reorganized my motors and found 9 of these old Strommies: 4 disc com and 5 standard versions. Here are the results of my extremely scientific survey.
Of the 4 disc coms, 2 were missing brushes so didn't work; one didn't work with the brushes and one started spinning, while making a beautiful electric arc across the whole furschluginer commutator!
Of the five barrel com versions, 2 didn't work, and the other 3 worked, decently. These were never speed demons, and I think the Mabuchi 15R may have been faster.
Happened to have an old Pittman in one of the plastic bags, so tested that too: started right up and spun smoothly.
So, draw your own conclusions: POS or POS²
Lots of these hanging around on ebay, in case you don't already have a dozen, so you've got options - but I think you're right, in that the later disc com version is not as good as the earlier version. It must have been a little cheaper to produce;
Don