I may be wrong, but I believe what Clinton was arguing for was that the entire case be suspended until he was out of office, the objection wasn’t simply to having to testify. The Supreme Court ruled that the case could continue, but the specific question of whether a sitting president can be compelled to give testimony in court was never touched on.
Not trying to be pedantic, and certainly not a Clinton-supported by any stretch. But I think the heart of this matter about the subpoena and a president did not actually get addressed back then.
With Obama the events took place before he took office. If he has information(which he clearly does) about the case and Blago's freedom is at issue, he will be compelled to testify.