I have both Merrill Moab Ventilator shoes and Merrill Moab GTX Mid boots.
I recommend the Merrill GTX Mid boots that look like the Ventilator shoes. They are the lightest DURABLE GTX boots I've found and mine are doing very well with about 500 miles on them. My Moab Ventilators have almost 1,000 miles.
You may want the Moab GTX shoes to keep weight to a minimum. I figure that when I need GTX I want a "mid" boot, which is barely a boot.
NOTE: on either Merrill shoe or boot I have reinforced the front 1/2 inch of the mesh (behind the toe cap) with SHOE GOO. This keeps the mesh there from fraying, as it otherwise inevitably will.
On a cleaned boot:
1. Use masking tape behind the area to be reinforced to make a clean line.
2. Color the reinforced toe area with BLACK permenant marker. (This matches the color to the toe cap)
3. Apply SHOE GOO to the toe mesh, keeping it off the toe cap. Work it into the mesh with your finger.
4. Let reinforced area dry for one day.