Splitfire advantage: everything plugs in and you only have to ground one wire.

Honestly for Nissan's you only really need one box, and that's a voltage amp. It basically takes the 12V your coil would normally run on and boost it up to 16-20V. That's what the blue box from the Splitfire kit does. The coilpacks are supposedly stronger, and probably wound differently. Even for KA's with a single coil, just wire in a voltage amp.

Here's a list of what to look for. Some are discontinued...
-Splitfire coilpack system SF-DIS-004 (SR20DET only)
-XS Engineering ignition amp
-B&M NewVolt ignition amp (the box, not the coil)
-Kenne Bell Boost-A-Spark wired to be on all the time

I've talked with customers running the KA-T's that have spark issues. Some of those guys don't know you need to gap the plugs down into the .030" range (stock is .044"). One guy did some research and testing with the Kenne Bell box and he's able to spark a .060" gap on high boost without misfire.

A hotter spark will get you better fuel economy and stronger driveability, too.