I like that Giant. I had really nice components and they use road components. 105 is excellent quality components. It's also geared more like a road bike. I would call that bike a flat bar road bike. The one think I don't like about the Trek (I hate mine too) is the rear cassette is 11-36. The spacing between the gears is too large and unless you are riding 15% grade all the time, you won't want something that low. The Scott has Sora components; those are road components, but are two levels below the 105. Unless you can get a really good deal on the Scott, I'd go for better components. Hybrid bikes will weight a bit more than road bikes; they are also a bit cheaper. In that price range you can probably might be able to find road bike in the 20 lb range if you shop around.

Ride each bike and see which one calls to you. Given the description of your riding style, I would say the Giant has specs that will fit requirements.