It depends on many factors. Short videos could be done quite well on nearly any Mac machine. Large to huge videos work better on a Mac Pro. The actual editing part, once you import the files is easily done on a lower end machine, its the rendering part once the video is finished does better on a multicore machine with more memory. Also video card may play into it depending on the video editor takes advantage of opencl or cuda for acceleration of realtime effects / import-export ect.

Really need exactly what you want to do with the videos, the length, budget ect. would be helpful.