The X-Terra 50 is lighter then the Explorer, easier to use than the Explorer, less tones than the Explorer, uses less batteries than the Explorer and even has less programing than the Explorer, so you can not do as much with the 50 as you can with the Explorer.
Now as far as disc the Explorer in the hands of a experienced person will out perform the X-Terra, but a person that has never detected they will find the X-Terra will work better. This goes for depth too as the Explorer is the top of the line in detecting and the X-Terra is not made to replace the Explorer, the Quattro or the Sovereigns, but to complement them with a lower price unit for those times you don't need the disc of the Explorer or the depth of the Explorer, but a easy to use detector at a decent price. We also see those that only get out a couple of hours a week max on Saturday and here is where the X-Terras are perfect for those that cant spend the time to learn one of the higher end detectors.
Now with that out of the way I have a Explorer, a Sovereign GT and the X-Terra 50 and have found where the X- Terra did get me a few coins the others missed, probably because it has a concentric coil and could see the coins in with the iron better. It is a good detector, but not one to replace the Explorer.
Rick