You're really talking about two things -- an electronic distributor and a multi-spark amplifier.
Points work just fine up to 5500 rpm or so. After that they have a real hard time keeping up. That's why dual points came along. But if you're rarely exceeding 5K and never exceeding 5500, the cost/benefit ratio of one of the high priced brands -- MSD, Crane, DUI -- just isn't there. However, a junkyard Ford Duraspark is so cheap that it's a toss up.
CDI spark amplifiers provide two benefits.
The first is that they fire a given cylinder multiple times over a range of 30 crankshaft degrees. But as rpms exceed 3000, they can't keep up, and the multi spark feature drops out. If you're running an extreme cam, any low rpm driveability improver is good to have. But if you're not, and you've got good plugs and wires and your carb is tuned right and your timing curve is right, then there really is no driveability benefit.
The second is that they step up the voltage to the coil. In the absence of a spark box, the output to the coil is the battery voltage, reduced by whatever resistance wire or ballast resistor that's in the circuit. This charge saturates the coil's core. The points open (or an electronic dizzie's reluctor or light window triggers the "off" signal) and the magnetic field in the coil collapses. This causes a high voltage to appear on the coil's secondary circuit and from there to the distributor cap.
The formula for this output voltage is V = L di/dt. L = the inductance of the coil, and di/dt is the change in current over time. Because "dt" is a very small number, V is a large number, from 20,000 - 30,000 depending.
An MSD box works the same way, triggered by points or an electronic switch. But the output of the MSD box to the primary of the coil is a couple hundred volts rather than 12 volts, giving a much higher secondary voltage output. This is why you can run a bigger plug gap with the MSD, and why blown engines like (require?) MSD's. And marginal engines with worn out components will run better too. But unblown engines in good shape, there's really no benefit.
Just look at any dyno test A/B-ing a spark box. AT MOST they pick up 3-5 peak hp; many show no gain at all.
On the other hand, there's this Ignition Solutions Plasma Booser thing that DOES give significant hp increases. Here's a link to a Mustang magazine story where they added one to blown 4.6 and got 11 hp and 11 lb-ft
http://www.mustang50magazine.com/howto/138_0307_plasma/index.html . Not bad for $300 and twisting a few wires together. I would seriously consider one of these if I had an extra $300 laying around.