It may be a little homerism
, but I also feel that Kearns has the most upside for this year. He will hit in the middle of the order for a Reds team geared to score runs and in a ballpark built for run scoring. Austin's age (25 in 9 days) and experience in the majors mean that it is now or never time for him to perform.
However, Jason did perfrom very well last year in the AAA, but it must be remembered that that IS the PCL (offensive heaven, so stats should be taken with a grain of salt).
Given the above, both are excellent options. Assuming both remain healthy I would definitely take Kearns over Bay. Injuries, however, have been a concern for the past year or so with Austin, so one must weigh the risk reward. For now, I'd take Austin and leave Bay.