The market capitalization of BNB is around $6.2B. UNI token is almost $4.1B; this is dependent on investor intrust and project worth; I think UNI will surpass BNB in coming days because UNI price is going to near future $100 so investors are investing in UNI token and will be soon above number 10.
I think your prediction seems biased. You just predicted based on capitalization both of token. UNI circulating supply is nearly 2x from BNB even BNB deceased many times their supply to increase the price. BNB first time record new ATH reached 50$. I don’t think as per as new player UNI will surpass BNB in short time.
Surely it will surpass the price of BNB very quickly, that's how the market demand is kept UNI coin. As of now the supply of BNB is kept burning on every three months, based on privacy and performance will defend their position in the market. Everything we need to wait and see.