Which one is going to require more power to turn?

Big blade would be best for a stock motor

Depends on diameter, pitch, and cupping. More of any 3 makes a 2 or 3 blade "harder to turn".
3 blade harder to spin than 2 blade if everything is equal. 3 more push than 2 at same rpm.

Probably get blasted on this-it has been my experience(with the ones I have personally used)-2 blade better in mud and is more "weedless". As far as speed refer back to diameter, pitch, and cupping.

Also, at least with outboards, blades can be manipulated to provide more or less bow lift.(rake)

All the above is also effected by hull design, length, width, and weight.

That is my 2 cents worth of worthless information.

well a big blade is 12x10p and a stock 3 blade is 11x10.5p

I'm modded with a .308 cam, heads, exhaust, mikuini and everything that goes with those mods. Rev limited to 4500.

I've run my rig with a Big Blade and know the results. I'm looking to see if the 3 blade will require less/equal/more effort to spin since is a smaller blade but a little more pitch.