Both finishes will give the titanium a darker look. A stonewash finish, however, would be smooth to the touch and a sandblasted finish will have a slightly rough feel, like fine grit sandpaper. A stonewash finish will also cause any anodizing to appear duller or more subdued.
This is mostly a matter of opinion, however, the random line anodizing looks great on a sandblasted or polished finish. For a stonewashed finish, a two tone finish (such as my blue denim, or lady liberty finish) looks great.