Difference between Performance Layer 4 and IP Forwarding (L3) Virtual Server?

you know why fowarding vs l2、forwarding vs l3、performance l4、standard vs was designed ?when you use more higher layer vs, it reduce your performance of device, l3 means you don't care what is in layer 3+ if it meets your needs。

eg：i must use performance l4 ，since forwarding vs l3 don‘t fulfill my’s needs ，i want to add some irule or l4 load balance , of course .then my need have changed,i need ssl offload,i need rewrite url, why not upgrade to standward vs ? performance l4(no pool member) and forwarding vs l3's funcation may be the same ,i prefered forwarding vs l3