Trying to see why the 731 grind is the overwhelming preferred choice when the 791 is the same specs but with 114 loa compared to the 731's 112 loa.
I will be running my exhaust out the prop so I'm thinking the 791 is the wiser option.
Am I wrong in thinking this?

Never even heard of the 168791 until now. It must be a newer grind. I doubt you'll see any difference from the 731 in power or reversion aspects.
IMO, its a waste of time to try and bump the hp with thru prop exhaust. It will choke off any gains in power.

the boat will likely be slower

Not trying to bump power. Its the overlap that is better for reversion.
In any event torque will still be better in the cruise rpm range. As compared to the stock cam I mean.
Its not a new grind. The Crane techline guy said its been around for over a decade and has also been the choice when dealing with the more respected marine engine builders.
I will most likely install a silent choice in the future so I will benefit further in the future.

http://www.cranecams.com/140-143.pdf

It will still most likely revert water with stock manifolds and the short stock risers.

I'm sure the Crane techline guy didn't give you any names of those builders.
No respected marine engine builder is going to upgrade to that cam and run stock cast exhaust. through the prop.

Im just going to put this in nice easy to understand verbiage....

Trying to run a perfomance motor with thru prop exhaust is like trying to drink beer and piss thru a coffee filter and wondering why you get wet.......

I picked up 731 Crane can with dyno time only and might sell it. I picked it up because it may have worked well enough with my stock valve train but since I’m looking at an extensive refresh I may go all the way to the 525EFI unit. It’ll be a couple weeks before I’m sure though.