The main difference is the inclusion of a milk frother: The standard CitiZ model is a standalone espresso machine. The CitiZ&Milk comes with an integrated Aeroccino milk frother. Both models have the same coffee-making capabilities. The CitiZ&Milk is slightly larger to accommodate the milk frother. The CitiZ&Milk is more expensive but offers the convenience of making milk-based drinks without a separate accessory. Choose based on whether you frequently enjoy milk-based coffee drinks.