I have the Jacobs E Brake and love it. It is easily my most used accesory. I believe all of the various brakes are good, but the clicking on a US Gears one drove me nuts. The 1 1/2 second delay on my brake was built in to allow you to have it "on" continuously without it actually cycling while shifting up a gear.
I installed the switch included with my brake cause at the time I didn't know any better... now I have the BD shifter switch. Its much handier.
Depending on what your(his) future plans are, the 4" brake under the body is worth considering. If he plans on going to a bigger turbo (HX40), that would be about his only option. If he is keeping the same turbo (or one of Piers new turbos!), I believe the brake mounted up in the engine compartment would be my choice.
The E Brake is an easy install. If you choose that one, let me know and I will send ya my phone number in case ya get stuck. Save yourself some money on labor.