Since the best sprinkler heads have built-in check valves, they are incapable of draining, no matter what you do. This means your quote won't have any of those high-grade heads.
Also, any system installed with poly pipe pulled by machine (no trenches) will not necessarily be pitched to specific drainage points, because the pipe pathway can have some rise and fall as rocks and roots are encountered.
Also, automatic drain valves can fail, and you won't know where they are.