It is more privacy for me. I trust my browser more than the app as we know many apps are sending trackers home which are used by big tech to track/invade our privacy.
Maybe someone else can chime in on the security side. My view is “httpS” in the browser and my VPN(which I trust, it is FOSS and verified) at the system level to protect.
I guess if the apk for my browser was compromised it would be just as bad as a compromised app.
This could help if unaware of apps “calling home” 
thanks to @river
EDIT: Sorry if I wasn’t clear. I also don’t transact using any pay services because this just gives these companies more leverage and control over me. This is why I love cash especially and also why others love crypto currencies. These things make us more free from my perspective (similar to privacy solutions like /e/).
*I am using my browser to check financial accounts, not transact. To see if you could transact via browser you would just have to try it out. The tech companies likely make it not efficient/user friendly as to be sure people utilize the app and in return can “call home” and collect data (maybe some personal bias here)