You need to decide how many speeds you would like for your whole house fan to cool your home.
Most manufacturers offer at least 2 speeds. Nearly all the hall ceiling mounted systems have 2 speeds.
The rafter mounted system suppliers have a much greater variety of options.
Airscape brought out a very high tech smart phone remote control in 2012 that allows you to control your whole house fan from anywhere in the world. Airscape then brought out the first and only 5 speed system and 6 speed system.
Invisco has just announced what the company calls “Ultimate Cooling Machines(TM)” – automatic speed control based on the temperature in your home.The SmartSpeed(TM) control runs the motor at full speed at temperatures over 85 degrees then as the temperature in your home drops under 85 the control reduces the motor RPM automatically. The motor slows down AND the power consumed drops down as your home cools to a temperature YOU select, from 60 to 75 degrees. No need for you to think about speeds any more. Just turn the fan on and let it do the work.
QuietCool has up to 4 speeds depending on how many systems you install. Their larger CFM units use 2 motors, each 2 speeds. Note that some of their systems ship wired as one speed so you need to have your installer change the wiring to take advantage of the 2nd speed.
Tamarack’s smallest unit, the 1000, is a one speed fan. Their larger systems are two speeds.
All of these higher technology sources offer a variety of controls including RF remotes and timers.