The Suorin Drop has the tightest draw on the devices that I've used. I really like the draw on the Drop. I haven't tried the Myjet so I don't know it compares. If I remember correctly, the Suorin iShare is pretty tight but the flavor isn't very good so I haven't used it in a while.
Both the Drop and the iShare have a silicone cover over the air intake on the pod. As you pull, the cover opens like a door and lets in air. I think that's the reason for the tight draw. In addition, the Drop has a silicone barrier on the battery that overlaps with the air intake on the pod. There's just a narrow opening for air flow on the silicone barrier and I think that further reduces the airflow.