I am not sure what you mean by dental based. All GPR's must rotate you through the ER/Medicine and Anesthesia. This takes up typically 4 weeks. Then there are usually 4 weeks of paid vacation. There are also 10 paid holidays. So knock out 10 weeks from clinic. During the other 42 weeks, you may rotate through OMFS, Special Needs, Pedo, so knock out some additional time from "comprehensive general dentistry", although technically it is still dental clinical experience. Add on some time doing emergency dental care. as you can see, the weeks of traditional care keep shrinking, and it is after all only one year. OMFS, Special Needs, and Emergency Dental Care are mandated by CODA, so they cannot be neglected.
With all this said, I would look into programs with enough chair space to accommodate all of the residents. This constraint will typically let you know if you will be on "extra" rotations in order to get you out of the clinic and free up operatories. Programs with many specialties attached can be favorable as you may be taught by boarded specialist attendings along with the specialty residents.
I admit, the AEGDs give a lot more didactics, but that is because they are still in a school. In a "hospital based" GPR, you will see more medically complex patients and have the opportunity to work and collaborate with other healthcare providers on a regular basis (physicians, nurses, social workers, etc.). Visiting and getting a feel for the culture of each institution is probably best. Visit before July 1. Too busy between July and Spetember.