DBPATH, LOGPATH and STORAGEPATH
It almost certainly doesn't really matter.  

The only significant I/O going to files in the database path would be to the recovery history file (and even that isn't much).  

Considering that DB2 uses the first storage path by default if you do not specify DBPATH ON, I would put it on /data if that was the only choice.

My SOP is to keep DBPATH in the instance owner home directory.  This is obviously another important location and perhaps makes more sense than the other two locations.