Would you kids be more motivated if it were on the computer? That might be an advantage for some kids. Online also has videos vs. text heavy information in the books.

We used the books first, tried the online version for a month, and then returned to the books. Having the text to reference, and being able to move around the workbook a bit works well for our family, and in that sense our experience with the online version was a little less flexible.

They are both good options though! I think you can go with your gut on whichever you think would be a better fit for your children, and change your mind later if you need to as well.