"As an owner that actually personally uses these machines, the latest OctoFrost IF Cooker, is the one I like."

Sinchai Luesukprasert, Marine Gold Products

As a user of both a steam cooker and the OctoFrost IF cooker, I am speaking from my own experience regarding these two machines (steam cooker and IF Cooker). A steam cooker is based on a forced convection theory which mixes air and steam to create the desired cooking temperature and cooking conditions. I loved the steam cooker when I first used it many many years ago (about 8) because it was very innovative in its concept and the possibility of cooking at lower temperatures was very new. It gave more consistency than my old cooker and was very helpful in creating quality as well as increasing profitability. I now have three of these steam cookers. The issue with this design, however, is that I find that the temperature hitting the shrimp is not necessarily the same as the one hitting the temperature probe. Also the air current is driven from fans on one side so the amount of steam hitting the product on the belt can differ. 
Years later, Harry from Innotec (now OctoFrost), came up with a new and innovative cooker (today - OctoFrost IF Cooker) that was able to combine the conveyor design of steam cookers and the precise temperature control of the water cookers. The belt design made cooking time perfectly controlled. The water showers created the precise temperature control and by using water, shrimps are evenly cooked through conduction. In a sense, this IF cooker can really control the temperature hitting the product.
You can set the temperature low and still cook the product at great capacities with is not possible with steam because the heat transfer rate is much slower with convection.
This meant that rather than a bell curve which means we are overcooking; this cooker can create a flat top curve by holding the shrimp at the desired temperature.
I am not sure if this is getting too technical but as an owner that actually personally use these machines, the latest OctoFrost IF Cooker, is the one I like. It is more innovative in both design and function and of course my cooking yield is better. This year there is a shortage of raw material in my country and I am cooking only a third of what I normally do. Out of the 4 cookers (3 Steam Cookers, 1 OctoFrost IF Cooker) I ONLY use the OctoFrost one. The investment is quite a lot but it was definitely worth it.