Lots of superconductors aren't very good superconductors. They have a low critical magnetic field which limits the current they can carry and the magnetic field

Lots of superconductors aren't very good superconductors. They have a low critical magnetic field which limits the current they can carry and the magnetic field they can produce. The liquid helium cooled niobium-titanium can make strong field and is easy to produce. The RBCOs superconductors, YBCO is the main one, are liquid nitrogen cooled and make even higher magnetic fields. It sounds like it took a while to figure out how make them in bulk. YBCO superconductors are going to be revolution but will take time for the older systems to disappear. Good example is ITER, which was designed for liquid helium magnets cause nothing else was practical at the time. The SPARC tokamak from MIT uses YBCO magnets which means it can be smaller, higher field, and cheaper cooling.