I will always recommend you to choose PGIMS over AIIMS Madurai mainly because PGIMS is a very old Institute established as early as 1959 while AIIMS Madurai is a new college and will take time to establish itself. Moreover, students of AIIMS Madurai have to study along with students of Ramanathapuram Medical College.
So, I will suggest you not to run behind the AIIMS tag.
Among these colleges, Madras Medical College is the best option. It is one of the oldest medical colleges in India. It offers huge case studies due to the patient load. The teaching faculties are great. The infrastructure of the institute is quite good. As the institute is located in the capital, it is more or less like a private medical college.
After MMC, the 2nd best option is Stanley Medical College followed by Madurai and Thanjavur. You will get to witness huge case studies at Thanjavur as it serves as a single medical college for three nearby districts.