Something that has a completely different function than another thing does not overshadow it.
This is the correct framing. Stablecoins are the digital delivery mechanism for fiat. Bitcoin is the exit from fiat. Asking if stablecoins will overshadow Bitcoin is like asking if better roads will overshadow the destination. The road gets you there faster. It does not replace where you are going.
At least you get it! A lot of the replies here are completely missing the point or introducing ideas or numbers that only confirm that they did not understand the topic. Even if stablecoins had a bigger market cap than Bitcoin for example that again does not mean anything at all, fiat's market cap is huge. While some countries are pursuing a nightmare of centralization known as CDBCs, maybe other places like USA can take a different path and try to digitize fiat with privately issued stablecoins. For now we have not seen large moves that suggest this, but they seem to like Tether and even more USDC.
As you pointed out, stablecoin like USDT are used more for transactions and payments. Meanwhile, we are using Bitcoin as a store of value.
Clearly, they are two different thing and serve different purposes. How can we claim that Bitcoin has outstanding advantages?
This is false, don't make up stuff. I never used USDT to make a single payment, I use Bitcoin for payments regularly. Do not interpret the world based from your limited experiences and data. People who choose to pay something in USDT would never have chosen to pay in Bitcoin because these are completely different things. Paying with USDT is almost the same as paying with traditional fiat. People who support Bitcoin tend to hate such concepts because they are a backdoor scam aimed at moving the masses away from the ideas of freedom.