pouët.net

I think that's just a differing viewpoint on what "assembly" is; his videos are more on a ground-hardware level that allow you to understand how a processor operates, which I think can be useful - after all, learning a new CPU architecture once you already learned another is just googling the syntax and mnemonics for pretty much the same tools ("what's arithmetic shift left called on this cpu?!")

MIPS is the easiest to learn. It was my personal enter into RE and I loved it for its simplicity. After getting pretty proficient with MIPS I looked at x86 and was damn shocked by its ugliness, redundancy and clutter. After x86 I decided to check ARM and hated its instruction set, which is pretty hard to memorize because of condition code suffixes, but I loved some of the cool features it has, MIPS could only dream about those.

Things are easiest to learn when you're motivated. People learn incredibly difficult things, when they're motivated. Why would someone be motivated to learn MIPS?

PDP-11, the one that started it all. It is a nice orthogonal instruction set and still a simple 8/16 bit machine.

Unfortunately there isn't much popular hardware running on it :(

If the decline of MIPS bothers somebody, RISC-V is rather similar.