Neither is exclusive of the other. I'd start with React, since it's 80% of the market. But, once you feel comfortable with that, move on to learning Vue.
Also, it's worth it to consider looking at Svelte. If anything is going to take a chunk out of React's market share in the future, it will be Svelte or something that looks like it.
Remember that there's no limit to what you can learn, one step at a time.
Neither is exclusive of the other. I'd start with React, since it's 80% of the market. But, once you feel comfortable with that, move on to learning Vue.
Also, it's worth it to consider looking at Svelte. If anything is going to take a chunk out of React's market share in the future, it will be Svelte or something that looks like it.
Remember that there's no limit to what you can learn, one step at a time.