Both Rho Cassiopeiae and Betelgeuse are massive stars that could potentially go supernova at some point in the future, but we cannot determine which star will go supernova first or when it will happen.
It's worth noting that Betelgeuse has received more attention and speculation regarding its potential for a future supernova due to its recent dimming and variability. However, it is still considered an uncertain event. Rho Cassiopeiae, on the other hand, is a luminous blue variable star, and while it has experienced significant eruptions in the past, the timing and possibility of a supernova are difficult to predict.
Monitoring these stars and studying their behavior is an ongoing scientific effort, but for now, we cannot definitively say which star will go supernova first. Supernova events are relatively rare and occur on timescales that can range from thousands to millions of years, making precise predictions challenging.