@Kitalon Speaking from my own observations in the market and my own perspective on this matter, I think the answer to this question highly depends on your exit strategy. But in the end, both options can be liquid when selling.
If we are talking about normal bullion coins: If the spotprice of gold should rise substantially; then like mentioned before: PM dealers (and rich people) will have less problems buying a 1oz coin from you. If you want to sell peer to peer in private however, not everyone will have the cash readily available to afford full ounces. As a result that the market pool you are selling to, becomes smaller.
Yes the premiums are lower on the bigger gold. So is it a okay to stack/collect fractional gold? Imo yes, even if they command a higher premium at purchase. Most often you will get the premium back when you sell peer to peer. And if gold price keeps rising over time, that premium will be easily surpassed by new all time highs. You will also have a bigger market pool of buyers when selling, because it’s more affordable for the average-money-making stackers/collectors in our society. Another plus is you can also liquidate smaller portions of your stack, depending on how much you want to cash out. Another important thing to keep in mind is the risk of loss during shipping (in case of selling peer to peer). Yes, even when tracked a package can get lost or stolen. For a lot of sellers and buyers, shipping a 1oz is much more stressfull and risky then shipping a 1/10oz.
In conclusion, in my opinion there is a future for both 1oz and smaller gold.