I'm not a fan of solder splices due to the brittle nature of the solder (truth be told, I'm not very good at it either). Vibration can easily lead to a crack that may not be visible when you are trying to troubleshoot a problem.
A good compression splice is the most appropriate for this situation, imho. Now a compression splice with a solder filler may be worthwhile but that may be a bit over the top.