What's the difference between Canon 5Ds and Canon 5DR? Which is better?

The difference is that Canon 5Ds has a low-pass filter, 5DsR has no low-pass filter, and the other parameters are the same for both machines. The price of 5DsR is slightly more expensive than 5Ds.

As for which machine is good, it depends on your needs. Canon 5Ds can reduce the appearance of moire as much as possible, but the resolution is not as high as 5DsR. Although 5DsR will have higher resolution, the probability of moire fringe will increase because there is no low-pass filter. If you require very high resolution (such as commercial photography), then 5DsR is very suitable for you. If you only shoot every day, 5Ds is enough for you.