In my opinion, this is just a prediction market, you can make money if you can predict the future better than anyone else. If Luna goes up in price and SOL stays the same, then you will earn money to buy SOL through LUNA. You'll also earn money if no one buys LUNA because their product isn't there or isn't that great. However, due to the risks of investing in any cryptocurrency market, even if Solana is not better overall than Luna, it is still worth investing in as it could still go up. It's all about the potential future value of investment alone.
This is why people are thorn between the two. In one hand you have a product (sol) that ended up doing something but not doing it greatly, they have tried it, it's working, it is "something" that you can look at or use, but it is not as great as promised. In the other hand (luna) you have a product that promises the worlds to you, but you have nothing in your hand, not really nothing but basically nothing.
So, which one do you trust, the one that has mediocre results? Or the one that could bring you something more than that, or maybe bring you nothing at all? I prefer SOL over Luna, but I also understand anyone who doesn't pick the same result.