Once serpents aren't as dangerous then the boat is the easiest option by far imo.

The cart stores a lot more but its fragile to larger enemies and building a good road takes some time and effort. It IS worth it though depending upon how many stacks you are hauling. And if you are carting through other biomes with other metal sources then you can steadily add more as you go using portals and rest houses to resupply.

I haven't tried the Longboat yet so I can't comment on that option.