I've owned every iteration of the MX since it came out years ago and have both a 4PL and an MX3X right now. The MX3X is a fine radio. However, I use my 4PL and love it. Aside from my 3PK way back when, the 4PL is my favorite. It feels right, has plenty of speed, works on 4 AA's (the MX3X requires 8), has tons of features and an outstanding display.

Truth be told, you can't go wrong with either one... but the 4PL gets my vote.