Yep, if the bitrate is the same then the lower resolution should have a higher quality image. The FPS confuses matters a bit. 4K has twice the pixels as 2.7K, but 60 FPS is twice the frame rate, so in theory it cancels out.

In reality I'd still expect the 2.7K@60 to be better, since video encoding relies on the differences from one frame to the next, so I suspect adding more frames is a 'cheaper' operation than adding more pixels.

I could well be wrong, though, and testing this stuff is pretty subjective ...