My favorite generators to service are definitely the John Deere powered SDMO. I actually consider it a good day when I realize that I'm going to work on one. Why? Here are the main reasons:
The enclosure. The SDMO enclosures are extremely quiet (around 60 decibels they claim) which makes a big difference when your running the thing on load for two hours!
The filters. The oil filters have a large lip on them with a big gasket so when you pull them off you don't even need a drip tray there is no mess at all. The fuel filter is the style that pops on and then a ring threads on and holds it in place (see the photo). Again nothing leaks out and any day you can avoid getting up to your elbows in diesel is a good one! If they have a racor style fuel/water separator a trick I use is to loosen the bowl before removing the filter so you don't get yourself covered in diesel while fighting with a bowl that someone probably over tightened (my favorite!!)
The drains. I'm a little too familiar with struggling with poorly designed oil or coolant drains for my liking. The drains on these units are all plumbed to the enclosure with a valve which makes it so easy (and clean) to perform the maintenance on and/or get your samples.
Fuel priming. This is a huge one for me! I've had coworkers complain that you have to pump the little thumb primer so many times (if you choose not to prefill the new filters with "dirty" diesel) but I would take a little thumb workout over struggling with a stubborn Detroit diesel fuel system any day!! I have never had an issue with bleeding a John Deere. The plastic bleed screw can be a bit delicate but if you don't reef on it like you do to your filters (grrr) then it should never be a problem:)
Oil fill. This seems like a weird thing to take note of. How hard is it to pour a jug into a fill spout? Very hard when there are wires and fuel tank vents and whatever else mounted directly in front!! I had to pick up a little 12v pump to fill some ridiculous units. The JD units are always right there easy to access.
There are always cons..
The only negatives I can think of would be the placement of the breaker. It's up high by the control panel which is a pain for the vertically challenged like myself. The other would have to be that the foam insulating the enclosure is so soft and squishy that if rodents get inside they chew it all up and make little mouse mansions out of it! The only reason this happens is if someone forgets to put a cap back on an access hole.
Overall they are definitely my personal favorites but I'm sure there are plenty of people out there who would disagree with me. Those people are what I like to call "wrong" :)