Besides safety they have the added benefit of significantly longer lifespans (charge cycles) compared to Li-ion. The downside being their lower capacity. The high capacity LiFePO4 in the reform are current 1800mAh (it might be 2000 on the new cells they swapped to after supply issues of the originals). Which is fairly low for a 18650, but not terribly worse than the 2500-3000mAh of li-ion 18650 cells.