I don't think there's a right or wrong answer here...your line up is fairly balanced, your stadium is a little slanted
Case for Ott:
1 - Better defense
2 - Can play an exceptable cf if Griffey goes down.
3 - OBA is usally .380ish and predictable.
4 - A little cheaper
Case for F. Robinson
1 - In a Polo or heavy BP park F. can get 55ish HR's
2 - He almost always outslugs Ott
3 - Better if there are any Hilltops or Minute Maid or their ilk in your division
So if it's a division with small ball parks or Yankee or Dunn, etc go Ott
If it's a division with lots of #HR's parks go Frank
If it's a tweener division like Tiger's Stadium, flip a coin
and then take Ott's defense regardless what the coin says.