I own two propane smokers that I've used extensively, and I have used the MES a few times at a few SMF gatherings. You should have plenty of O2 to run propane, just make sure you have a steady source that you don't have to drive far to get.
The disadvantages of propane are ensuring you have enough for a long smoke (for example, I can get about 30-35 hours on a 20lb tank of propane, so I have to take that into account before starting a long smoke on half tank). Also temp control can be a little hard without a needle valve installed. They don't really blow out in steady winds, but winds will cause temps to fluctuate. Other then that the maintenance is actually very little.
The disadvantages of electric are they usually can't go much higher than 275, which is a bummer for doing poultry. Also, for some reason it doesn't do a good job making smoke, so in other words, the first thing you have to buy after purchasing an electric smoker, is a device that generates smoke.
Also, power outages equal no smoking, so ensure you have a dependable grid. It's also hard to get a nice smoke ring on stuff you cook, (but that's just for looks really). Sometimes the heating elements needs to be replaced and the electronics too. Lastly, my biggest turn-off about electrics is they look like giant microwaves, but it's just my personal opinion. There are like a million MES users on this forum and they will probably disagree with me, but I still support them b/c anything that promotes BBQ and smoking in numbers like that is a good thing to have!