Circulated Coins

Welcome,

It depends on the individual coins since eye appeal is part of grading. Its possible a coin with no luster could look better than one with luster and some scratches and the reverse it also true.

Thanks, is it is a matter of opinion I would go for the coin with no scratches and no lustre as I have seen a definition "original design remaining". I guess a scratch is a defect in the original design.

And lustre in a coin can be a result of polishing.

An original luster and minor scratches would probably be AU-50 if it's minor scratches. Otherwise it's a details grade.
No scratches and no luster is an almost certain details grade (as it was probably cleaned), but a possibility of a MS details one. Alternately, it could be a honest VF-35 (or whatever they call one step below XF - possibly VF-30) with all the minor bumps that ever were there (if any) worn away; if there never was much of a design (Wyoming quarter anyone?) and/or this particular type wears slowly it could also look "near mint quality".
I don't know whether AU details trump VF-35, or indeed whether MS details trump non-details AU. It's in the eye of the beholder. I personally would rather buy the scratched coin if it's not too ugly (indeed an 1907 IHC I have is a good example of that - it has a huge rim bump, and would never get anything but a details grade if ever sent for grading, but the bump is not distracting [to me anyway] and the coin is otherwise very beautiful); but even more likely, I'd try to find a decent VF-20 (or even, if we're talking AU-50 versus MS details, a decent XF-40) and save the rest of the money for some other purchase

Polishing is, normally, quite obvious in that the "shine" extends onto the devices of the coin. This is not something one would expect from original surfaces. At an extreme, one can also see "smearing" of the lettering and such.

This is all an area where unfortunately the only salve is experience - looking at coin after coin over a long period. Further, consider that coins of your country - in fact, pretty much anything not produced in North America - are graded on a much stricter scale than their US counterparts. The 70-point Sheldon Scale we use here in the US is generally not applied to World issues.