If the unit is going somewhere you will look at it every day, buy the Stylish. It is the only one offered in three finishes, the only one you can have in silver, and at 189mm deep it is the shallowest box of the five.
If the complaint about air conditioning has always been the draught, buy the WindFree S2. It is also the cheapest way into a properly installed system, and the quietest figure any of these manufacturers publishes.
If the wall is tight, or the unit is going above a door, or the budget is doing real work, buy the Comfora. At 770mm it is the narrowest indoor unit here.
If you are fitting more than one room, or you want one range to cover a study and an open plan ground floor, buy the Perfera. It reaches 7.1kW, and unlike the Comfora, which reaches the same, it brings the sensors and the Flash Streamer with it.
If you care what is inside the box more than what is written on it, buy the ZS.