I would prefer to put my money in a regular bank over a co-operative union any day. In a co-operative union, if u know someone who is higher up in the hierarchy then its relatively easier to get a loan and not bother paying it back.
Whereas in a bank there are safeguards which can be broken, but the depositors are protected. Look at the recent failures of co-operative banks in India. Any financial institution where the power to disburse funds lies in the hands of a select few with no accountability, is doomed to fail. Banks are accountable to the Reserve Bank of India.