Hmm, both very mellow pieces. Hylian Lemon's has more going on though and had some exiting pieces which is always good even in mellow pieces.
Hard Day's Night, as has been said, did great with mixing the two themes. You combine them in places, making a new melody. Problem is, when that happens it is hardly recognizable (and I didn't find I liked this one nearly as much as the themes on their own). Despite that, it's high quality integration of the themes, and feels very cohesive. Just what I like to see! I loved the overlapping from 1:23 - 1:48. Very polished piece. However, looking at the backbones of the sources, I kinda feel like we didn't get a whole lot of creative risks. We get lots of mixing which is really cool, but overall, it just feels really mellow. Quality, but not a whole lot standing out, either.
I like how we've gotten a quite a bit of exploring of Spring Man's theme in a variety of tones. Orchestrated and psuedo rock/electronic with solar man. However; light, happy and cheerful is where it really belongs. Hylian Lemon takes that to the moon (carrying along an adamantanium spring, of course) And Hard Man is explored with that same tone, making for a really interesting, uplifting piece. It's cohesive and quality, on par with the competition. However, it's got the creative uniqueness that I think was missing a little from prophetik's. 2:37 - 2:45 was really creative, with 2:46 - 2:56 being even more so! I think Hylian Lemon's done the most cohesive covering of the Spring Man source, so props for taking all of it. 1:15 - 1:25 hasn't been touched on a lot, and it makes a great transition to Hard man (while clearly keeping both sources)
I vote for Hylian Lemon for having a little more creative feeling piece.