2 and 3 are my favorites, however I think I favor 2 because it seems like the tree is much sharper and I like the yellow with grey skies. With the more blurry tree and too-intense blue sky as mentioned, it drops a notch. The only qualm I have with #2 is that it looks like you pulled the clarity up all the way ( most notably on the tree ) so it's casting a shadow on the left side of the tree over the landscape that is miles away. I suppose this could be intentional and desireable to some for that certain effect, however, personally I'd try getting rid of the shadow with curves, lightening up the image and then just masking the shadow area trying to blend it with the rest of the landscape.
Several wanted to see the base of the tree - here's one that I just processed from RAW ... This one better? BTW, the wife picked #3 so far, but she hasn't seen this one...
I do not like the effect on number 4. I bet that's a nice shot without all the post-bells-and-whistles.
#2 is the better of the bunch. As others said it has clarity to it, I can feel the bark on that tree. Also you've got nice sky, without any (unavoidable) blown out clouds. It has a dark quality to it that I like. That's your shot right there.