From what I understand, antimicrobial peptides are roughly grouped into three structural sets, with large variations present between different groups as well as within the groups. Their anti-microbial properties tend to be through slightly different avenues than traditional antibiotics as well, since they can effect cell wall structure and some intracellular targets.
I have been told that antimicrobial peptides are thus able to be effective against as larger spectrum of organisms and that said organisms develop a resistance more slowly.
I do not understand why either of these cases is true, since any antibiotic sharing the same target should have the same effectiveness. Also, evolutionary pressure is what drives resistance, so why should that be reduced against antimicrobial peptides?