Drop-in tubs fit inside a frame and can fit anywhere in a bathroom, while recessed tubs, sometimes called skirted tubs, are set in an alcove and surrounded by walls on each end. A recessed tub project is usually less complicated.
Installing a drop-in tub requires the building of a deck or ledge to surround the tub and special plumbing for the faucets and drains. The installed tub is supported by the sub-floor, which must be reinforced, not the tub ledges. High-end bathrooms often have drop-in tubs installed next to picture windows.
Recessed tubs are the most commonly used style. This is the type found in tub/shower combinations, with the faucets and shower controls located on the wall above the drain. These tubs are found with or without an attached tub surrounding it. This gives homeowners the choice of using tile or other materials for the walls surrounding the tub. The all-in-one models tend to be less expensive and easier to install.
Drop-in tubs are more versatile, giving designers more leeway when coming up with bathroom layouts. Recessed tubs work well in smaller bathrooms where there is not enough room for a separate shower, or where rerouting the existing plumbing is not feasible or prohibitively expensive.