To be fair, your bank was right. Anything Android based is a massive security risk.
that is a over generalisation of the situation and wrong , all electronic transactions carry a risk even on closed systems like blackberry and iphone and even Xbox or ( as we well know ) PSN , as most successful exploits now involve a lot of social engineering nobody is safe on whatever system they use for the transaction .
As it is i only use my linux box for electronic transactions which is a lot more secure than the equivalent windows box , not completely secure but a lot more secure than any mass market electronic device for the simple reason , not a lot of home linux boxes means very slim picking if you went after them as a hacker " .
Rogue apps have been a problem on android but not for long as the community is self policing and its very easy to spot a rogue app and even easier to load up one of the many free security apps .
As already said , a lot of hacks use social side of things and go looking for the naive and gullible , that as said , are at risk no matter how they do their E shopping but i will concede if you are the aforementioned a closed system would be safer .