I have an ME-20b and wouldn't be without it. The single stomp box route is paved with expensive mistakes. I only need octaver and chorus every now and then and sometimes I like fiddling with delay and wah but I know I'll never use them in real life.
Patch cables, pedal boards, cases, batteries, power supplies etc etc. Very expensive and time consuming. It's also a lottery seeing home different pedals interact with each other. If you really care about your tone and you're after somethings really specific, then singles are the only way to go.
If you want to learn what effects do and how they work then a multi-fx is ideal. In one box you can experiment with phaser, delay, chorus, wah, octavers, drives, synths etc.