Short Term Ladder, yield question

[mukramesh]

I am currently using a directly held short term treasury ladder (maturity 1-3 years) for a portion of my cash. When purchasing new treasuries, once I choose the maturity date, should I just try to pick the one with the highest 'Ask Yield to Worst'? For example, for treasuries maturing on 11/30/2016, these are the current yields:

0.508
0.519
0.52

Granted the range isn't that large. But is there ever a reason not to go for the one with the highest yield?
Additionally if there are treasuries that near the desired date but have a higher yield, is it more worthwhile to select those?

I guess this same question applies to the Bond portion of the PP.