I am just saying that in any instance a larger diameter shaft is alway stiffer and stronger all other things being equal. If you are trying to keep precision machined gears precisely aligned under extreme load, that larger diameter deflects less.
That's not true n this case. .....and once again this is splitting hairs, but let's split them completely, shall we? The 489 is not the strongest, because it uses a crush sleeve. That in itself is a weak point. With a crush sleeve eliminator, it's a different story, but stock for stock, the 742 wins out of the three.........even if just barely. You really need to understand the 8.75 as a whole in order to make a statement about them, because their strengths are so close, that any of the three could fail under the exact same circumstances.
In short, it's simply not a difference worth arguing over. Yet here we are.