Really depends on how well the sporterizing was done. I'd go out and shoot it if it doesn't shoot well then you have an action to play with. I've got two sporter M1903 rifles that I bought one in .35 Whelen and the other in .338-06. Both rifles shoot better than I do.
Better do some research. I understand that N O guns are made of GI parts with a N O receiver on them. Some have shown up at gunshows and they wanted near what a real 100% GI gun was going for. Pretty sure that the receivers were not good quality like Remington or even S....whatsername, the typewriter makers. A sporter made on their receiver would have to be pretty cheap to justify it.
The national ord. guns are guns made from left over parts after they quit making them. As far as shooting goes there fine, they just don't hold a high value as a original military issue gun. Since it has been sportzerized it really dosen't matter anymore.