I have run my Caddy similar to this way for the past couple years. The Caddy has a two speed fan limit switch and I would run it on low speed during the coaling stage. Fan speed 2 was my "normal" setting and fan speed 1 was my "low" setting. The fan speed controller is much better in my opinion because it is all automatic. My low speed fan was tied into a switch and sometimes I would forget to turn it on or I didn't want it run all night etc. The only pro that I could think of is that you are using the low speed factory setting and not monkeying with the motor voltage. Earlier in the thread there was some talk that the speed controller could possibly lesson the life of the blower motor.