Paterson (or the knock-offs). They are deep, oversized so that the prints aren't crowded and have wide grooves to get fingers/tongs under. For film developing they are my only choice; smooth bottoms for no scratches!
Yes, you can get other trays that work just fine, but if you are buying your first batch, just get the best. There is a big difference in trays. I've had some would barely fit the size paper they were intended for. The Paterson (and Cesco dimple-bottomed) trays are generous in dimension. And, at Freestyle's prices you don't even have to try to snag used ones on auction sites.