I share your intuition. Absent credible evidence to the contrary, I would not use anything on Windows other than the default from Microsoft. On the other hand, I probably wouldn't expend a lot of energy arguing with Grandpa when Grandpa has decided Grandpa knows better.
However, my first level advice would be not to do banking online, but that's another story.
However, my first level advice would be not to do banking online, but that's another story.