I don't know if you want to be an academic or enter the business when you study finance in the future. First of all, talk about academics. If you do theoretical finance, you may learn pure mathematics better, provided that you are really good at it. But the mathematical foundation of statistics is not bad. In empirical finance, statistics is much more practical than mathematics, because the econometric model used in empirical research is based on statistics. Moreover, the number of people who do theoretical finance in this world is estimated to be less than 20% in academic circles, and it is rare in China. It is often done by double doctors in mathematics, engineering and finance. You should be prepared for this.
If you enter the industry, then the math requirements are lower. You don't need any advanced mathematical knowledge when you work. On the contrary, counting this kind of applied mathematics may be helpful for you to engage in the financial industry.
Generally speaking, if you really want to devote yourself to theoretical finance, then I suggest you choose pure mathematics, and it is not limited to undergraduate courses. Undergraduate mathematics knowledge is simply not enough, and compared with statistics, it does not reflect your professional advantages. In addition, if you choose to make a financial demonstration or enter the industry in the future, I suggest you study statistics. To tell the truth, for a well-educated science and engineering college student, finance really has no mathematical difficulty. I rarely think outside of mathematics and think from a financial point of view.