The Atlantis resort in PG is not bad, but it's right off the Sabang beach area which is a dump (others will argue this point, but that's because they clearly don't know "a dump" when they see one
Dumaguette is significantly better, but other than trips to Apo Island, it's virtually all macro diving. If you enjoy this, it's awesome - we've been 3x times and will go back again. Their dive operation is also really good... Last, the Dauin coast (the area where the resort dives) is truly the "frog fish capital of the world" during the right time of year.
Neither location will give you much of a shot to see whalesharks (feeding or otherwise). There was a whaleshark spotted last season cruising by Apo Island, but it was just passing by. They do run full day trips to Oslob where you can share a whaleshark experience with hundreds of your closest "friends" (which is probably what you heard about).
You will see quite a few turtles along the Dauin coast (and definitely at Apo Island).
You won the trip, so you need to decide what kind of experience you want. PG has good over all diving, with the resort close to bars and restaurants. Dumaguete is a bit more remote (but not off the beaten path)... you'll definitely see more turtles in Dumaguete (esp. around Apo Island), and the variety of critters is (much) better in Dumaguete (but the dive sites are a little less varied - you're basically diving the same coastline from north to south).