Yes it can be better than soldering, because if soldering is not done correctly it can overheat the wire and cause it to fail, and it can also trap air in the solder which is a GREAT insulator. As for being solid from the factory, have you ever looked at a bike? Those plugin connectors on the speedo, signals, taillight, etc. They are all crimp-on connectors. The things that are soldered are usually connections onto items like reg/recs and the like. I have done lots of wiring, so has my instructor, and so has my boss and all of us are of the opinion that if a crimp is done correctly, with the proper tools, it will provide a better connection. I've seen it time and time again.
Another point to consider is the ductility of the wire. If you heat the wire and add solder, the solder can "bleed" down into the wire and when it solidifies, it is just that, solid. No ductility. There's a lot of twists and bends on motorcycles, and if that solder breaks, it can damage the circuit and cause issues. Another thing is that MANY MANY people use the wrong type of solder. Most hardware stores sell hundreds of different types of acid-core solder, because it's cheaper but on motorcycles (and other vehicles for that matter) that are open to the elements, acid-core solder easily oxidizes. Acid core is not meant for electrical connections. The only time it should be used is on mechanical connections (ie. attaching a ferrule to a cable). Rosin-core solder should be used on electrical connections.
I have used solder in the past, and on some things it works great, but I prefer proper crimp connections on anything I do, and I'll stand by my electrical work 110%. Do I still heatshrink, of course, but I stay away from solder whenever possible.
I hope that clarifies my stance on the position
PS Haelo posted before I was done this, plugs are still crimped and can easily be disconnected as he stated. If you're breaking a connection that's crimped, sure you'll cut it and lose material. But if you heat a soldered connection, and break it lose, you'll never get rid of all that solder and you can again, destroy the ductility of that wire. Technically if you want to break a soldered connection you should cut that as well and start fresh, same as crimped.