Joe,

I don't know if it is genetic or not but we both came to NAT with plumbing problems this evening! 

I vote for the compression fitting. Every time I have tried to solder a copper tube with water in it or partially drained it has been a problem. maybe the Shark Bite fitting will work, I am just not familiar with them. If this inside a wall behind a shower you want something permanent.

Good luck.

Dad