If oxidation is a concern, there are many solutions available that don't make the wire so stiff that it won't conform to a simple connector. Soldering typically reduces the contact patch versus not tinning as the wire can't crush down and shift about to accommodate the shape of the hole that it is in.
Solder is very pliable. In fact, it's more pliable than large gauge copper. Another reason to tin the wire is if it is stranded, it prevents loose pieces from not making it into the connector and possibly contacting something they should not (like ground).