Good information. Honestly, the thing that I noticed the most in terms of difference between Cube and 531 is that Cube doesn't do much to make life easy in terms of setting out the program. Sure, you get your main lift sets and reps and your progression, but then you still have to faff around with what bench and DL variations to pick, what assistance, etc. With 531, at most you have to pick a couple of assistance exercises.
I know that makes me come across as lazy, but of I'm using a program someone else has written I want to have minimal mental input into it. Otherwise, I might as well just keep writing my own program.
I can probably sum it up best by saying that I read Cube twice and the programming part thrice and was nowhere near setting out even the first week. I read 531 once and within an hour had twelve weeks' worth of training set out, including the assistance work I picked for myself.
Granted, for someone who thrives on high volume maybe neither option is good but for me who works best with moderate to low volume 531 looks like such a great way to learn how to separate the training wheat from the chaff it isn't funny.