First lets clarify something about core materials, and that is protection level. All core materials will protect you equally as long as its lead equivalency rating is .5mm (which is the industry standard).
Regular Lead Material
You want this material if you are wearing your apron for short periods of time and don’t mind carrying around extra weight on you. It is also the least expensive of the materials. However, when you go to dispose of it you will need to send it out to a recycling facility that offer a lead apron recycling service.
Lightweight Lead Material
You want to select this material if you are looking for the best balance between weight, cost, and durability. Since this material does contain lead, it must also be disposed of properly at a lead recycling facility.
Lead Free Material
This material is the best solution for those professionals that have to wear an x-ray apron for long procedures. Since this is the lightest material even saving half a pound in weight can be significant when you have to wear it for a 6 hour procedure. The other benefit to this material is that since it does not contain lead it doesn’t have any special disposal requirements and can be simply thrown away, when it is ready to be retired.