He carried a spare tire, spare lug nuts, and spare wheel bearings - not just plain bearings, mind you, but grease packed bearings inside a complete spare trailer wheel hub. He was prepared for the worst when it came to trailers.
Perhaps he was overly cautious, but be sure - he never had to get help with his trailer. Actually, the way he washed and greased everything on the trailer, those bearings would never be used. Since 1995 they have been sitting on a shelf in my garage, all packed and ready.
His paranoia about salt corrosion is completely reversed in other people. They don't take care of their float-on trailer, and after a year's service, they wonder, as they sit on the side of the road waiting for a tow truck, why the bearings are gone.
So which trailer is actually better? Arguably the winch-on will last longer if you never get the wheels and axle wet with saltwater. But, the float-on trailers can last just as long with proper care.
Aluminum I-beam float-on trailers are almost the standard anymore. Protective covers, special axle seals, and grease fittings keep saltwater out of the bearings if serviced properly. A little soap and water and a high pressure hose will break the salt up and help stop the corrosion. All it takes is a little work when you return from fishing.
I have a freshwater river close to my house and right on the way home. So, when I return from a local saltwater trip, I stop off at the river boat ramp and back my tires into the water and completely submerge the axles and rear part of the trailer. I pull up, and back down several times to get a washing action going. I get a lot of strange looks from the local bass angling folks when I do this and then just drive away. But the washing action helps displace the saltwater with freshwater, and saves washing time for me.
The answer to the original question becomes one of time and discipline. If you have the time and discipline to wash a float-on trailer every time you use, it, I would go with a float on. It's so much quicker and easier to launch and retrieve your boat. You younger folks with strong backs can use the winch - even an electric one - and pay less attention to the trailer. But for me, washing a trailer is a whole lot easier than winching a boat by hand. Give me a float-on any day!