Iowa,
The best treatise I've read on this is Jeff Hibbard's book "Baja Bugs and Buggies". It is far and away the most splendid "how to" book I've ever had the pleasure to read.
If you'll permit me to summarize what he says at the risk of getting something wrong:
The swing axle suspensions are far more robust. However, when jacked up and modified (tuned) wrong he says they can have you upside down in a heartbeat.
I have a '70 baja project with an IRS suspension. I have come to the conclusion that for me and my plans, if I can only have one, I'd want it to be IRS.
However, I want one of each. One of the niftiest rigs to my eye is an early swing axle car with a king pin front suspension and an early bus outboard reduction gear boxes and a bus transaxle. Although this would make a bone crushing highway cruiser it would make a great off road car.
VT