Broadly speaking, there are 4 different kind of ACs for growers.
Portable Air Conditioners: These are the small-sized air conditioners which you can move around with ease. These usually have wheels on the bottom and tend to cover a smaller area compared to the other kinds of air conditioners. However, these are considered to be the best air conditioners for grow tents and are great for growers who have lesser number of plants and a smaller growing area.
Window Air Conditioners: These are age-old devices which you might have seen in some older buildings. A number of growers continue using these because of two reasons - first off, they are cost effective and cost almost half (and even a third in some cases) of what a regular wall-mounted split AC would cost. Secondly, they are easier to install as they can just fit right into your window. They, however, are noisier and consume more electricity as well.
Split Air Conditioners: A split AC is one of the top options that growers have when it comes to choosing the best air conditioners for grow rooms. Split ACs consume less electricity and operate silently, and tend to cover a larger area as well. However, they are much more costly when compared to almost all other types of ACs and getting a good split AC might set you back by $700-$900 easily!
Ceiling Air Conditioners: Ceiling air conditioners are meant for extremely big growing areas such as if you are growing in a greenhouse or if you are growing across multiple rooms. These are piped ACs which hang from the ceiling. They are rather complex to set up and most growers who grow in grow rooms or grow tents would rather avoid them.