You are questioning my statement that Lowrie is the better player. Assuming both are about an .800 OPS short-stop, Lowrie's offensive production is better because it is predicated on making fewer outs. Just to see what I'm talking about, let's use the 1.7 conversion that has been determined to get OBP and SLG on approximately the same scale. Also, I'll extend the assumption to include that Hardy is a .330/.470 and Lowrie a .360/.440 (this is in line with what they've done in MLB and MiLB to date).
Lowrie = (1.7 x .360) + .440 = 1.052
Hardy = (1.7 x .330) + .470 = 1.031
Now, keep in mind this is on an adjusted scale. MVP caliber season's typically end up .400/.600 or better, and .400/.600 is 1.280. The difference is not large, but it's big enough to not ignore. Lowrie is the better player.
Furthermore, this ignores the fact that a) Hardy has not had one MiLB season that came close to Lowrie's from last year, and Lowrie leads Hardy by .070 OPS points this year.
Yes, I realize you are talking about having them on the same roster, and my original point still stands. Why do I care if we have both, if a condition of having both is that Lowrie, the better player, is the backup? You posit that 90-100 games out of Lowrie is an easy number to hit with him as the backup. Big deal, 150+ with him as the starter is better.