I think this is a really general question. Answer to this depends on what your location is and what your requirements are. Split air conditioners are broken into two important parts, the inside air handler and the outside condenser. Hence they take up a little bit more space compared to window. Window air conditioners are easier to install compare to split. But split air conditioners are more aesthtic and beautiful compared to a window unit. Moreover, you will need a big hole in the wall or a window, to install a window ac. Split ac can be hung by the cealing, concealed inside the cealing, hung on the wall, installed in the wall, and much more. So it would definitely be based on what your needs, and what are your restrictions.