I might play the devil advocate here... but if I were you I think I would get the Fountain tarot AND the Wild Unknown.
The Wild Unknown is quite unique, and I think the most "edgy" of your list. I find the imagery beautiful, and it reads beautifuly, with a different take on each card.... the images has a way of sparking my intuition in ways that are quite different from other decks.
The The Fountain tarot, to me, is a collection of 78 beautiful reproduction of modern art, and also it is easy to read. I like its "coolness" - it has a sort of remote quality, like it is speaking from higher in the air or something. But still very clear.
The readings from the Fountain are quite different from the Wild Unknown ; even if you pull the same cards from both decks, I find that they have a very different voice. And, both those decks are very good quality cardstock and come in beautiful nice sturdy boxes that will stand the test of time. I love shuffling them, their thick and smooth cardstock win my heart. The Fountain is a real experience of luxury for me... this elegant mattness, the gilded edges, the box that is the color of the inside of a delicate shell, and when you clasp it shut, it makes a soft thumping sound.... its really something.
I do not have the Linestrider so I cannot really speak for this one, though the images I saw on Google are definitively "edgy" IMO. It does look like a very beautiful and different deck, and from what I gather, it gives interesting interpretations of the cards. For some reason, though, I have the impression that I would find it less easy to read than the WU and Fountain, but I might be wrong of course.
The Shadowscape I do not have either, but I do not really think I would like this one - from what I have seen of it on the net, I find the images too whimsy, too busy, too uniform in colors.... I feel like I would have a difficult time identifying one card from another, and identifying what they represent - I always have to squint my eyes and to think for a moment, in order to understand what is on the images I am looking at. But once again, I am only speaking of what I saw on Google for this one. I would need to see it "in the flesh", to make a proper opinion of it for myself (and who knows, I might surprise myself by falling in love with it if I saw it in the flesh)
I realise I am not a great help, and that you did not ask to be given the advice to aquire several decks ; so I apologize ! But for myself I would not be able to chose between the Wild Unknown and the Fountain. Sorry !