I have been doing the same, I've wanted a diesel dually for years, but never could justify it. The S-10 and Ranger have done all I needed of them, and only on a couple occasions over the years have I wished I had something larger. Both are paid for though, and I have absolutely no need for a truck that large. A nice 1/2 ton would suit me just fine.
Diesel fuel is more expensive than gas, though most diesels get nearly as good as mileage as my 4.3L 2wd S-10 (it drinks gas, so much so I thought I had the CPFI spaghetti tube leak, but no fuel pressure loss, guess it just uses it). Cost of ownership is much more expensive, one can easily spend a couple hundred on fluid and filter changes along with the aforementioned two extra tires. Parts cost more (hope you don't have to change injectors) and are not as common, everything is bulkier and heavier when you do have to work on it and you'll need a stepladder to get to some parts of it. Not small space, drive thru, or parking lot friendly. Wayyy too long at nearly 22' and it takes an airport runway to turn around in, along with having to make wiiiiiddde turns. Too wide for many small roads, those tires and fenders stick out there really far. It's noisy, the diesel exhaust smells, and is probably way more truck than most anyone who buys one ever really needs.
How's that? lol. I've told myself the above for years now.
I bought a new to me 2007 GMC Sierra 3500 LTZ crew cab 4x4 dually long bed with the LBZ Duramax / 6 speed Allison last week......
It'll look good pulling the 12' jon boat... :lol: