Full metal case FMC or as I am used hear it called, total metal jacket TMJ should be ballistically very similar if not identical though they differ in the manufacturing process and often the price by a significant margin. The main point and advantage of the full metal case/plating is to reduce lead exposure to the shooter which can be dispersed in the air around you when using FMJ with the exposed lead base or completely unjacketed ammo. If you shoot indoors often this can be a real health concern or even outdoors if you do a lot of shooting.

Hi Robert and welcome. This is a case of six of one and half a dozen of the other. Pros and cons of each are not very different. This article gives a good explanation. https://nij.ojp.gov/nij-hosted-online-training-courses/firearms-examiner-training/module-10/composition#:~:text=Full%20metal%20jacket%20%2D%20encloses%20the,point%20or%20a%20hollow%20point.

ammo cases come in brass, aluminum and steel. brass is the best it is reloadable and easier on your gun. FMJ is Full metal jacket which is lead bullets with a Full copper jacket you can also have steel core, full lead, coated lead and many other bullet types. Many ranges will not allow steel core ammo