My preference is to crimp, then solder and then use a heat shrink rated for underground usage.
I agree.
Either one by itself will create the necessary area of contact for electrical flow with zero resistance. Protection against corrosion is mandatory.
If it's done right. The number of ways you can screw this up is infinite, based on what I have seen professionals, and jerks that think they are pass as fine work.
Check the temperature of the terminal and wire after a run. If it isn't at ambient, then something is wrong.
The boat guys have been fighting this for as long as electrical circuits have been around.
Solder vs. Crimp: National Marine Electronics Association standards state that solder shall not be the sole means of mechanical connection in any circuit (with the exception of certain-length ship's battery cables). If inclined to add solder to a lug terminal, solder it after you apply the crimp. A good solder joint is bright and shiny.
If you see corrosion on the wire replace the wire. Don't screw around with cutting back to "good" wire.
A bad solder joint or crimp joint looks like . . . Oh, hell. Do the homework.