First of all, the Snapdragon 888 supports 5G, while the Snapdragon 855 can only achieve 5G functions through an external baseband. The difference between the two processors is about three generations, and the frequency difference is still more, but the Snapdragon 888 has no processor heat dissipation problem!
Snapdragon 888 is a 5nm process, while 855 is 7nm, and 888 is also the first Snapdragon integrated 5G processor, while 855 is a processor 3 years ago, which does not support 5G communication. So 888 is at least two generations ahead of 855.