I don't have a savings but an investment account. Doesn't make sense to me to sell my investments slowly to cover for monthly payments.
If we were talking a car I would've agreed with you but I'd rather pay upfront for such smaller sums and get on with it.
As far as effort, if it's a high-yield savings account you should be getting one of those anyway, and then the phone-specific effort is a single transfer or doing nothing at all. And the financing itself is probably negligible.