No experience with the PL-12AC. I had a PL-12D and later a 112D which is the same as the 115D except no arm return. Both sounded fine except for slight motor noise. I have a slight preference for the PL-12D because the suspended chassis of the 112 would occasionally bottom out when really digging in with a record brush. Since I didn't have them at the same time, I obviously didn't do direct comparisons, but can't hear any major differences in cassettes made with either one, that I could attribute to the turntable.
The Dual question is more enigmatic. Belt drive vs. idler and all that. Although I've never owned a Dual, many friends have and I have a soft spot for the 10xx and 12xx idler drives. The 1225's smaller platter weighs against it but not that much in my opinion. But the 503 was also well regarded in its day.
Out of those 5 choices, if condition is near perfect, I'd probably go with the PL-12D. But any of them could make nice music. And auto-shutoff can be a handy feature to have.