CIS is a world unto itself. It is "similar" to no known (at least to me) EFI system in the world. There are people who have spent a lot of time on this board on CIS tweaks. Similarly, there are people who have gone to EFI. Dollar independent, I don't think there is reasonable dispute that a properly installed EFI system is superior to the most geeked-up CIS system imaginable. But you can get pretty impressive performance up to the limits of CIS, and it is certainly less expensive than most if not all EFI systems.

Luckily, as discussed in this thread, you have a bunch of stuff you can do now that doesn't require you to weigh in on either side.

For background reading on Porsches, buy yourself a copy of The 911 Performance Handbook, by Bruce Anderson. Good discussion of the basics of Porsches (including the CIS years) up to the 993tt.