I doubt that there is much difference from a performance standpoint ... the raid 1 scenario would presumably require a tiny increase in system resources. Raid 10 would appear to be a little easier to manage in as much as you would be dealing with one file rather than two. If I remember correctly, fragmentation statistics aren't accurate for multiple files either.

The above all assumes that the 2 files are across one filegroup (as that would use the proportional fill algorithm) - if one were to split the database into two filegroups (one file per filegroup) then there are other potential advantages from the raid 1 scenario .... filegroup backups, partitioning etc etc.