Like Bob, I once preferred soldered connection. Alas, the technical consensus today is that for many applications crimp connections are superior.
Solder does insure good connection, but also causes embrittling of copper wires since copper gets hardened by slow cooling, and softened or annealed by fast cooling. It's the opposite of steel and iron. So good quality crimping (with the proper crimp tool) is often a better choice, especially when vibration is present and the individual wire strands are not so large as to assure non-breakage with continued mechanical stress. With a soldered connection, there is a big mechanical stress riser right after the edge of the terminal, where the wires are no longer supported by the terminal. With vibration stress, this is where the wire/strands will break off over time as the heat hardened copper succumbs to stress cracking.
This is the reason you will find virtually no soldered connections in the automotive engine compartment. They crimp to reduce costly in-warranty troubleshooting and repairs.
It is strongly counter-intuitive to think that a crimp is better, but were there is vibration, it really is...just because of the very odd tempering characteristic of copper.