It's the shock loads that are the issue. Those shock loads when the halyard is 'tight', magnify the total load on the halyard. They are much higher than the simple static loads that you'll want to resist. The difference in capacity is about adding about 1/2 going up from the captive key to the #1495.

The splice costs about the same, you're only talking about four beers difference ;^))). ($10, or so).

Is your problem the screw shackle vs. the little pin?

My two cents worth: If you're trying to reef the main in on a windy day, the last thing you want to happen is the halyard shackle come loose -- especiall with a captive pin tha could get bent more easily than a larger screw-in pin.

The larger shacke looks like it will scratch your mast less and makes the splice chafe less. You may need a thimble to make the splice work on the #91434? What does that bit of SS cost?