Diffuser for DIY CO2 Help

I have a 60 gallon fairly heavily planted tank. I am running 2 hagen CO2 ladders hooked to 4 cannisters. I want to change the ladders (as they detract from the aesthetic) out to 2 of the CO2 diffusers shown here: http://www.greenleafaquariums.com/co2-diffusers.html

But I am having trouble deciding on which ones. I am trying to get as much equipment out of the tank as possible so smaller is better. The inline jobs are just too expensive. Suggestions please. Thanks in advance.

Dave