The Modern Key Dates..

IMO the top pop premium examples are the riskier of the two options but they are also the ones that can have the biggest payoff. If you can get them cheap I would definitely go with that option but if they are already expensive there is no guarantee that they will increase or even hold their value.

Theyre kind of a tricky series to judge to me. Yes their mintages are generally small, but so is their collector base. It wouldnt take a whole lot of increased interest compared to other series, but I'm not sure that increase will ever come. Out of everything in mint sets they have to be the least popular.

I do kind of like your idea though of searching mint rolls for the best ones and getting those graded if the already graded ones have a steep price. If you go through enough you should be able to find a few gems comparing them to each other and if not you still have exactly what you started with in terms of money. Theres really no risk until you actually send them in for grading