But any contact between two conductors affects the overall resistance slightly. Again, it's just intuitive to think that a connection made by heat and melting metal would make for less resistance than a connection made by only pressure. Otherwise, why are so many other connections in electronics (wires, circuit boards, components) soldered rather than plugged or crimped?
I actually don't solder the sleeve. I use epoxy and shrink tubing to hold things in place.
If it works for you thats all that matters I guess. To each his own.
Seems like more work than just crimping it, but the tooling can be a little bit of an investment at first.