My choice would be the first one but not for the specific reason you mentioned. When I think cluttered I think of a lot of stuff in the photo. Since that's the same for both shots I wouldn't define it that way. What makes the first one better to me is you look and feel like you are outside and a part of the beauty nature created. The second one is still just as beautiful but for me is constraining like I'm inside a building looking out and cut off from what I'm looking at. I like the feeling of being a part of the photo rather than just taking a quick peak out of a window which the border creates. The goal of any photographers should be to draw the viewer into the picture and if possible make them feel they are there. In the first one you have accomplished it well and no kind of frame can improve on perfection.
By the way, is that a covered bridge on the right or a small shelter maybe for waiting on a bus?