I currently use the B1X, which is the hard plastic version of the B2.1U. I use it ALL the time!! To me, even if the effects are set at the same level (say 80 which is unity gain), some sound louder than others. However you can easily adjust them one time and save it to memory. You have forty locations that you can save to and forty permanent ones. I program my favorite effects all in order so I can get to them quickly with the up and down footswitches.
It has a pretty good built-in tuner that I use when needed. Funny thing though, I bought it with the drum machine feature in mind.....and I don't use it

Go figure.
I love both the effects (wah, distortion, fretless etc) and the amp modeling features. I don't know anything about the ME-50B so I can't comment there.