Hot Air is older and traditional, been around for about a decade. IR is relatively new in the reworking market.

Hot Air gives uneven heating. IR provides more even heat due to absorption rather than penetration thus a simple benefit of IR is it can remove plastic components, such as a CPU socket. With IR it penetrates the solder joints and does not burn or melt the plastic. IR is usually silent in operation because it has no air flow, while Hot Air uses a forced air system which is heated.

Technically speaking a Hot Air rework station is more complicated to manufacture than IR in structure and the cost is higher. This is because there are many cables in top hot air heater along with with a fan system. Hot Air uses nozzles which is both a pro and a con. The con is you have to purchase different nozzles for different sizes of chips. The pro is that nozzles can be rotated in 360 degree which is very easy for alignment.

Infrared BGA rework stations tend to use ceramic heating plate. They give even heating without causing shift of other surrounding components due to the lack of air movement. Due to the IR plate being a fixed size, you may need to use high temperature tape to cover the surrounding area of the BGA chip. However when using Hot Air you may come across the same issue if your nozzle is not an exact fit or the air flow is too high.

Many of the expensive machines use Hot Air because, well, its been around longest and many companies do not want to switch. They have procedures in place and changing them will cost too much. Samsung or Intel with several millions of employees having to retrain and re certify them is too much. Why do you think so many companies still use Win 2K or XP, its all about the transition cost and time.

IR is newer, but it is gaining much more interest. The reason it has a bad name is due to the inferior plates being used. Higher end plates such as those fitted with Elstein heaters will perform much better. Such as our ACHI IR12000.