Uncertainty in op-amp propagation delay?
If you BW is only 45 MHz at unity gain with a wide tolerance, you cannot expect Prop. delay to be stable or accurate between any two devices in the xx ns range.

How would you like about 100 ps accuracy or less? 

Choose a CML (current mode  logic) comparator instead.
http://www.analog.com/media/en/news-marketing-collateral/product-selection-guide/Comparator_Brochure_07.pdf

e.g. www.analog.com/media/en/technical-documentation/data-sheets/AD8561.pdf

t_pd = 6.75 ns nom  @5V @25'C  8 ns nom. over tmep.