Being an advanced artificial super-intelligence wouldn't be that bad if you acquired a proper mobile unit, armed to to the teeth for roaming the wastes. Also, you'd likely be a pre-war government project, so you'd get to live through the pre-war days as well. Maybe you'd just have an army of remotely controlled robots, and be on an advanced mainframe. It would likely be difficult to acquire/produce such a unit that is powerful enough to hold an advanced super-intelligence far beyond the human mind, but still have proficient combat ability.
Obviously, given a choice of immortality, I would take it. The thing about being a brain in a jar is that your brain can't last forever, it will eventually be too old too preserve with the most advanced technology.
Being a prime human made super mutant may not be that bad except for the discrimination, maybe.