I have a JC kit that I enjoy. It works well, and it's simple, too. I've seen the SMC kit, and it seems like a good buy, too. It allows you to tune from inside the car, and you can adjust turn-on points and pump speed. Nice.
The SMC pump is mounted inside the tank. If it craps out, it's not easily replacable. The tank itself is industrial plastic, or something like that. The JC tank is aluminum, and the cap is engraved with the power 6 emblem. A nice touch, IMO. Some may argue that the tank is too small, but it lasts long enough for me. The JC kit came standard with a braided alky supply line. I've heard that early SMC kits didn't have this feature. Later kits I've seen came with this upgrade.
I agree that the SMC controller is rather intrusive into the passenger compartment. To me, it's actually an eyesore.
While it allows a lot of tunablility, it really sticks out unless you hide it somewhere.
With the JC, you just adjust your turn-on via the Hobbs switch, select the proper size jet, and you're ready to go. I've added a small light to let me know when the pump is running. I mainly like this kit because it's simple, easy to install and work with, and doesn't take up a lot of room on the car. Maintenance is easy, as parts are readily available and servicable by the owner.
No flames intended for SMC guys. Just offering up my opinion.
Steve