It's hard to say. I like the tree in the second shot just because of the contrast of the bark and the sky and it's crystal clear. But i think i like the second to last shot... even though the lighting is a little off. It's really hard to get the lighting just right with such a bright background. I think you did a fantastic job.

I do think the 3rd is probably the best overall for all the reasons you mentioned. Keep up the great work. =)