In theory, the antennas will give you the same gain. Yes there will be more noise recieved with the omni's due to the 360 deg pattern. One note however: vertical beam on the 7dbm omni will be around 10-15 degrees (or less!). On the directional it should be 30-50 degrees. This will make it harder to align the narrower beam on the omni's. They will have to be at the same height, or if at differing heights, they will have to be tilted to get their narrow beams to line up. I would choose the directional antennas over the omni's.