John Brownlee for Cult of Mac notes that Apple’s tech specs page for the new iMac indicates that memory on the 21.5-inch iMac model is “configurable” up to 16GB, while the 27-inch model sports “four user-accessible SO-DIMM slots.”

An important consideration for anyone weighing the differences between the two machines. You’ll be stuck with what you get on the 21.5-inch model, while you’ll be able to expand the 27-inch iMac to up to 32GB as you need it.