Rib cartilage is a viable source of excellent cartilage for performing revision rhinoplasty.
Ear cartilage can be used as well, but ear cartilage is limited in how long of a spreader graft that can be made. Depending on how thick your spreader grafts would need to be, there may also be limits to how thick ear cartilage-based spreaders grafts can be made. The cartilage can be sandwiched to widened the graft. To get enough cartilage both ears may need to be harvested. With rib there is such an abundant supply that typically just one rib needs to be harvested.
Ear cartilage is weaker than septal or rib cartilage. I haven't found this to be as much of an issue with spreader grafts alone. However in revision rhinoplasty cases often the cartilage is used for more than just the spreader grafts. It is with these other uses that having strong cartilage is very important. I suspect that if two surgeons you've consulted with suggest rib, that is part of the reasoning.
Potential risks of rib grafting specific to that technique are injury to the lung during harvesting and warping of the the cartilage grafts. Lung injury is quite rare. You would want to make sure that your surgeon is board certified in facial plastic surgery or plastic surgery and has experience in harvesting and using rib cartilage for revision rhinoplasty cases. Board certification alone doesn't mean that the surgeon necessarily harvests rib or uses it for rhinoplasty very often.
The chance of warping can be minimized by using specific carving techniques. I have found that carving the cartilage incrementally over the course of a few hours (so warping can declare itself) allows for excellent results. If one needs straight cartilage the central core of the harvested rib is less prone to warping. If there are external deviations to the nose, however, one may want some curvature to the spreader graft to help straighten the nose.