The Jusnes kit is a better bang for the buck in several ways. First Bob is a R-F member and you can talk to him. He's a good guy and has a better price. There are also more folks here that have his kit and can give you specific tips.
Having said that.. I bought my fan and controller back before I had the ranger. I've used thier products on several other cars because IMO it's a top quality product line.
I bought the largest flex-a-lite "S-Blade" fan they have and their controller kit through summit. I think it was right at $200 or so when I got it about 4 years ago.
The fan is very quiet and smooth. Most of the time I can't even tell it's running. (no joke) That's why I put the blue LED light on the left side of the radio bezel!
Thier controller is a very very nice piece. It allows you to fully control the fan as well as run the fan at slower speeds to reduce the power consumption.
When the fan kicks on because of heat, AC, or in cab control it ramps up speed based on need. Only drawing 17amps max. It only runs at 60% to begin with and will increase in speed as needed.
As far as mileage.. IMO unless your towing and/or in the south you won't really see a increase from the e-fan. I didn't. It does however make the motor a bit smoother.
The underdrive pulley IMO is the second best bang for the buck on a ranger. Most definately worth the money. Better power and better MPG with out a doubt. My pulley web page
My K&N web page
Best bang for the buck in power and MPG is a X-cal 2 programmer.