Some of the links on this forum allow SMF, at no cost to you, to earn a small commission when you click through and make a purchase. Let me know if you have any questions about this.
They will both do the job, however the MES will operate at lower temps than the gasser, in case you want to make some sausage or bacon. On the other hand the Master Forge will get the temp up to 300+ for poultry, so you get crispy skin. If I had to choose one I would go with the Masterbuilt.
Just my humble opinion... Al is right about the MES holding lower temps than the Master Forge... but one thing you can do to the Master Forge is install a needle valve/control valve after the regulator. Fairly cheap mod and simple too. It really allows you to adjust the temps lower than with just the valve on the smoker itself. It also allows for finer temp adjustments. The Master Forge also makes a great cold smoker if you get yourself an AMNPS, but then so does the MES. I think they're both fine units....let us know what you decide!