So, what is the difference between this ball linear guide and the roller linear guide?

The biggest difference is the different support methods between the two:

The support body of the ball type linear guide rail is a ball, and the contact with the slide is point contact (divided into two point and four point contact types, of course, the more contact points, the better the rigidity, the higher the manufacturing accuracy, and the higher the cost);

Roller type linear guide rail (cross roller guide rail) has a support body of rollers, which is in line contact with the slide. Compared to the ball type, it has higher rigidity and greater bearing capacity. However, one problem is that its travel is limited, unlike most ball types, which can be spliced for very long lengths.

Relatively speaking, the ball type has the advantages of lower cost, faster speed, and longer splicing; The roller type has greater bearing capacity and better rigidity under the same volume.