Everyone's eyes are different. Some people see frame rate as more of an issue, while others want to see finer details. It is your choice what you prefer.
Increasing the resolution typically makes aliasing less of an issue. However, it is still an issue. Some people might find they can get away with 1x or 2x MSAA at 2160p, but may need 4x at 1080p. Others may find 2x MSAA sufficient at 1080p. Increasing your resolution 4 fold results in a big hit to frame rate, not something that I personally would want.
Do you notice a difference when increasing MSAA? If you don't then don't worry.