The Outer Island seems better suited to your 140 pound weight. There are quite a few messsages in the archives on the performance of each kayak.

I have built and paddled both the Night Heron and Outer Island in varied conditions, so I offer some comparisons below. I have tried to keep the comparisons as objective as possible, but are necessarily from the perspective of a 155 pound paddler typically carrying 10-20 pounds of gear in the boat:

PADDLER WEIGHT:
NH is intended for heavier paddlers than the OI. Assuming a 40 pound boat, the NH is intended for a 210 pound paddler, whereas the OI is intended for an ideal paddler weight of approximately 160.

ROLLING:
The rounded/shallow 'V' and lower rear deck of the OI gives it an edge in rolling, but both are quite easy to roll.

STORAGE VOLUME:
The NH (even the low-deck version) has more volume in the hatches. Both boats are sufficient for a weekend trip.

EFFICIENCY AT NORMAL PADDLING SPEED (3.5 knots):
Not much noticeable difference to me. The OI creates less bow wave and yaw on each stroke.

EFFICIENCY AT RACING SPEED (5.5 knots):
The OI seems slightly faster for me.

STABILITY:
The NH feels more stable on the water. Both boats have sufficient stability for a touring kayak, assuming an experinced paddler.

MANUVERABILITY:
The NH turns much easier. Someone that likes to play carving turns and seeing response to strokes would probably prefer the NH. The OI is a much stronger tracking kayak, which can sometimes disappoint when playing in tight spots.

WIND:
Neither boat has a problem with weathercocking if the weight is properly distributed. The NH drifts downwind faster than the OI.

QUALITY OF PLANS:
Both designs come with full-size templates for the mold. No tracing with carbon paper required.

BUILDING PROCESS:
The NH can be easily built on an internal or external strongback, whereas the OI is most easily built on an external strongback due curvature of the boat and low volume. The NH was a little easier for me to build. The deck strips near the sides of the cockpit were the most challenging, as the take a radical twist.

APPEARANCE:
Both boats are real lookers. The OI has a much stronger Greenland look to the profile.

John