In the new 6 kingdom system of classification, like the old 5kingdom system, organisms are basically grouped by

They are grouped according to features which are thought to be of biological significance.

The rate that would change would be the  searching efficiency/attack rate. there are only two other rates in this model: the  growth rate of prey, and the  predator or consumer mortality rate.the  searching efficiency/attack rate is what indicates how effectively can a predator capture its prey whether in the searching process or actual capturing/attacking process. 

There are  advantages  to being  multicellular  rather than unicellular. these include allowing: the  organism  to be larger.