I have 2 dependants at uni ,is there any benefit to claiming their tuition credits all on one parents return ( the higher earner) or dividing it between both parents?

The tuition transfer credit is non-refundable. This means you only get it if you need it to reduce your taxes owing. If you don’t have taxes owning, you won’t get the credit. If you only have some taxes owing, then you'll only get enough tuition transfer credit to reduce your taxes to zero.
 

If you have two children transferring their tuition, a single parent may not have enough taxes owing to take both transfers. You may need to transfer one child’s tuition to the other parent.