Several reasons for crimping over soldering, soldering requires special tools and the right solder, also requires a certain amount of skill and preparation, I have seen cold solder joints, aslo seen were somebody used acid core flux on solder on control install. I have a T&B crimper and a set of Ideal wire stripper crimpers.
What I did was solder my connections to the existing harness, and staggered the connections, so the connections were 3/4 of a inch apart vertically, and taped my OEM plug for the regulator. The second, and most important, and this applies to everything including crimps, I increased the surface area of my connections, that is the wire striped was 3/4 of a inch long, the harness conductor insulation was striped about 3/8 of a inch, so I got about three wraps around the harness conductor, before I solder it.An increase in surface area translates into a increase in conductivity.
I use the T&B on both insulated and non insulated, I also have a crimper for insulated 10 gauge crimps on my Klein linesman pliers.I can honestly say that the ring of the crimp will break before you pull the wire out.
If you have the time and knowledge, I can honestly say my solder connection is superior to almost any crimp, the exception is when you get into larger wire sizes.
At one time the standard for crimping was to use a set of dies and hydraulic crimper specific to the wire and crimp, aluminum and copper. In both cases, a proper crimp using a Burndy tool would show the die number on the crimp, if the die number didn't show, that was a indication of a faulty crimper. In large wire sizes, there are long barrel and short barrel crimps, it is important that the wire is free of oxide, that applies to soldering as well.
As to crimpers, they now make die less crimpers, about twice as fast as hydraulic, and much cheaper-------------another subject no Biker ever needs to worry about. JMH