[magnets]

When crimping, you want to end up with a connection that won't come apart, and a big mass of metal that has no air in it. Whether this is done with a really good crimper, or by soldering, it will be OK. A good crimp can't be pulled apart by hand.

The idea behind the no air spaces is the same reason why a cold solder joint isn't good. You want the solder to melt and to go into all the little cracks and form the mass of metal that will conduct electricity just like you want all the strands to be pushed together really well.