DL,
I have to agree with Stu & Steve, if you are looking at buying a boat, the better choice is diesel.
From a safety standpoint, there's alot less pre-checks starting your engine. Remember gas fumes are heavy and will settle low in your engine compartment/bilge areas.
Folks with gas need to be in the habit of checking for fumes & leaks before start. You also need to make sure the exhaust fan is working properly. Then there is that fuel cost.
I use my battery charger on a timer; boat is at a dock year round. Say a gas leak developed while unattended; say your bilge pump is set to AUTO.
This can be a problem.
Light a match & throw it on a can of diesel. It will not ignite, it takes pressure in the cylinder to make it ignite. That is really the only place you want spark.
As for fuel quality, I never get it from fuel docks. I have a Mobile station near me that has clear diesel, what you would call aviation grade. Four 6gal. jerry cans fill the tank. Over time "bugs" suspended in the fuel will die-off and settle as sludge in the tank. This can cause your filters (primary & secondary, always have 2) to clog. This will always happen at the worst possible time. Joe had it happen to him.
It happened to me at a critical time. Afterward, I cleaned my tank, new filters & good fuel. not a problem anymore. If you decide to have a survey done on the diesel boat, make sure you have the surveyor check the fuel pickup for signs of sludge on the screen. It may also be an option in re-negotiating sale price.
Hopefully the diesel boat has the better selling points.
CR