I am clearly a diesel bigot and believe that diesel Mules are the only way to fly!
Gas engines are not bad, but do not have the fuel economy, the power, or the durability of a diesel.
Diesel can set around for months on end, start right up and go to work. Gasoline engines gunk up the carburetors and have all sorts of problems when setting around for only a couple of weeks to a month. So, they take special care with how the fuel is kept fresh, how it is treated to keep it from forming gum, and still will require carburetor work from time to time because of the low quality of gasoline that is available.
Diesels have far more torque for loading and pulling, so make a far better ranch unit than the gas rigs. I can pull a ground driven John Deere 12 foot windrow/tedder rake with one. That sure saves a ton of time when doing small hay fields or clean up after the bailer has been through and there are chunks of windrow still left that need to be consolidated.
I also load up over a 1,000 lb of hay and go feed with a diesel rig. Yes, I am way overloaded, but it works great and saves me the expense of running a tractor or truck. I also clean stalls, haul produce, hunt, and just have a blast with the diesel rig as it is flexible enough to do it all.
It does not blast around at 45 mph as does the brand X gas rigs, but I never have had anyone hurt running a Mule at sensible speeds, and can allow the grandkids to go out without any particular concerns for their safety. Also, how often does one need to go faster than 27 mph anyway? Most running is around 3-9 mph.
Also, if you have a wife that likes to "supervise" the expenditures, it is far easier to put them on a Diesel Mule for a day and have an ardent supporter of your choice of rigs than it is on a gas rig that does not do nearly as much work for the buck. The down side is that the diesel Mule will end up doing yard and flower duty all summer long because the wife will latch on to them because they are so easy to start and use, so you will need to buy her one of her own!