For investment purposes, BTC is a better bet than Monero. But from a privacy standpoint, Monero will still win, because it is way more decentralized than Lightning Network. I have a feeling that Monero will still be widely used, irrespective of how much BTC takes off as a viable payment option.
That's the problem. People just hold BTC unless they need XMR for privacy reasons, that's the only time they convert their BTC to XMR and only for the small amount they need to buy drugs or whatever purchase. As far as investments defi coins are killing it because of rewards and compound interest. Let me use a newly released airdropped defi coin Songbird ($SGB) as an example:
You get 100,000 SGB airdropped. You immediately stake it for 3% interest per week. If this interest rate can hold you've doubled your stack in 24 weeks. After 52 weeks your stack has 4.65x'ed and if price also appreciated then your gains have gone up in the double digits. The drawback is that 3% interest will go down as time goes by but if it can average around 2% for even 6 months your stack would up to 170,000 SGB and add price appreciation to that and the gains become ridiculous. If interest averages down to 1% you've still increased your stack by over 30% in a short time frame.
Meanwhile XMR has stayed under $500 or maybe Bitcoin went up and it also appreciated in price to $1200. Defi coin would still win out because of rewards in addition to price appreciation. XMR 5x'ed while SGB will net you 8-10x returns in the same period. The only real downside of defi is that these coins have no utility. People are just buying them for profit but once the market goes bear these will all go to zero and when that happens it won't matter how much rewards you've accumulated. With XMR there's a level of comfort knowing it will continue to be a relevant top 50 coin with both utility and similar scarcity to BTC.