The me50b is a whole world away from the me20b.
I've used both.
The 20b was one of the worst pedals I've ever used, plastic, nasty, hard to use and sounded awful.
The 50b is much better made, much easier to use due to the individual knobs and sounded far better.
I realised I don't use enough effects to make it worthwhile.
For me, individual pedals will always sound better once you've spent a fortune finding the ones you like.
Big disadvantage is the romance you have to do to change sounds.
Pedal board she sound good if you get a good one, and once you find the right sound you can save it as a patch for one click changing.