No one knows. For speed, try credit card. The reason buying Ether can be slow is because the traditional banking system is very slow. Whereas many Bitcoin buyers use the coins to send money internationally, most Ethereum buyers appear to be buying ONLY for speculative purposes. That, however, does not seem likely. Buying Ether with a bank account will allow you to save on fees, although it takes longer than buying with a credit card. Fiat exchanges make it easy to withdraw ETH by simply selling and sending the proceeds to your bank account.