Iris all the way. We have 54 racks that use Iris tubs and a few misc racks with sterilite the girl who washes the tubs gets 5 or Iris tubs clean in the time it takes to clean out 1 sterilite tub with all the grooves and feces seem to stick to them much more then the Iris tubs do. Plus Iris has no plans to change the size of the tubs anytime soon. Sterilite has changed the tub sizes 4 times in 5 years. Save yourself the headache and go with Iris in a few years when you can't get the sterilite bins for your rack you'll be glad you did.

Off the topic I know but if your buying racks go with www.reptilebasics.com racks can't be beat for the price and there customer service is beyond top notch.