the diesel should last longer. But considering how long the Honda motors last I can't see paying the hefty price for a diesel. Unless you are going with something larger than 24 hp
Diesel is a different animal than gasoline motors. There is a formula that will explain the difference what Torque will do for you in a pressure pump situation. You may be able to use less HP from a diesel than Gasoline engine. Plus the diesels are heavier built. They have to be due to all of the compression ratios and huge amount of torque.
Look, its like a Ford vs Dodge. Ford has the same torque more or less as the Dodge, however the dodge is at 90% max torque at idle. Fords 90% torque is at 2500+ RPMS.
If I am facing up hill with a trailer at 15,000 lbs, The torque at 900 RPM's will engage the drive without ridding the clutch to get going. The Ford will need to race the engine to the max Torque to gain momentum. This will damage the clutch or the torque converter.
The Ford ACTS like a gasoline engine.
On a smaller scale, your Honda will put stress on the engine when ever you start it up with a load. Belt drive you will have no choice. You will also burn two to Four times as much fuel. On our 90+hp turbo Diesel, with under a full load, twin pumps and 4k generator going, we burn 1 .2 gallons per hour. If we use only 1 pump, we use even less, about 7/10 of a gallon per hour. The diesel is also at a lower pitch and is quieter than a 24hp Honda. Even our 90+ hp is quieter than the 18 to 24 hp Honda's.
Another note, we have a Kubota diesel 28HP ? ( I think it is 26 to 30 HP )
This engine have 3,000 or so hours and was bought in 1992. It is on our filter. Still running strong with NO maintenance issues..... EVER. Not so much as a oil leak. Thats 17 years same motor. Can a Honda under a load last 17 years with no maintenance issues. Just change the oil ever six months.
Its like this.... pay now twice as much or pay in a few years for maintenance issues.