If wanting to sell, what venue would you use? If eBay, I'd bet it would also be a fine starting point for comparing. Still, and I'm certainly not making any suggestions one way or the other, it's always wise to keep in mind that you're comparing a single transaction to multiple, so even if individually had the potential to bring more of a return, you need to ask yourself if worth the time, hassle, and increased chances of a headache. Good luck either way.
As a buyer, I would be more likely to buy the whole set instead of just one coin. That's just me though.
Some are after just one coin, but slabbed, and normally PF70. But that a guess to get it slabbed and hope for 70s. You may want to just research eBay and see how they sell as a set, versus individually, versus slabbed individually 69v70.