Over at dpreview you can simply select the Sony A7-3 review then compare the image to the Sony A7R-3 using comparative resizing. The differences seem very likely to be visible in print, especially at A2 size.
Additionally, what results from downsampling a high res image is also an image that is "easier" on the eyes than a straight bayer conversion. Less fatigue, which may be an entirely subconscious experience, but possibly more relevant than can be expressed in some objectively quantifiable property. Most of us would like a print exactly because it is a far more relaxed method of viewing than a monitor viewing experience can provide.
The other question that might be relevant though is: are you prepared to purchase the appropriate lenses when opting for the hr camera? Sampling a mediocre lens at higher resolution merely makes the lens deficiencies more noticeable, but obviously doesn't provide a better viewing experience.