From the perspective of someone who works on low voltage electronic and communication equipment, and doing board level repairs - A proper crimp is ALWAYS better than a soldered wire connection, especially when in an environment subject to vibration and movement. The problem is that many people, unknowingly, are doing absolute crap crimp jobs with poorly made tooling and connectors. Combining the typical "do-it-all" auto parts store crimper and parts store level (or worse, HF) crimp terminals will just about guarantee a bad crimp job.
Look at just about every OEM wire connection out there - none are soldered, they're all crimped. Even on the super sensitive modern sensors where a couple hundredths of a volt one way or the other can be a big deal. Sure, it can be argued that the OEMs are cheap, and soldering costs more, but that's not the reason. Fact is that a _proper_ crimped connection is just flat better both mechanically and electrically, than a soldered connection. A proper crimp will create an air tight seal around the wire, essentially creating a "cold weld".
Soldering is essentially gluing the wire to the terminal with a filler that tends to degrade over time. Electronics techs are familiar with this, and having to "reflow" circuit boards over time. Many back yard amateurs aren't soldering these things correctly either, causing damage and poor connections. Soldering also causes a brittle zone that will lead to future connection failure if the wire isn't strain relieved correctly.
All that said, if you're using the $5 parts store crimpers, with equally cheap connectors/terminals..yeah, you'll probably end up with a better connection electrically speaking if you drop some solder down in there too.
