I gotta say that I love the colours in the first photo. I don't think there's enough to grab me in the B&W conversion but in the colour there are some subtle yellow tones in the tree that contrast against that lovely blue sky to make it really stand out I think. The clouds are another detail that is lost in the black and white but they seem to delicately wrap themselves around the tree to highlight it further - especially how the lines in the clouds criss-cross to pull your eyes to the tree.
I'm not normally a fan of the leafless tree shot but I really love what you have here