I took a listen to some of your Nightwish audition stuff, since I'm generally a fan of them. Very good! I enjoyed Walking in the Air much more than Nemo and I think your style is more suited to that song. Nemo seems to require a more classic vocal sound, at least if it's to retain the original Nightwish feel. That said, your rendition is an excellent cover
Your voice works great with the acoustic guitar; I just had a hard time imagining it backed by the heavier sounds that are in the original recording of Nemo.
EDIT: I gave both a listen back-to-back to try and pinpoint what the main difference I was noticing was. I think what it comes down to is your vowels more than anything else - in order to fit with the full sounds of the original recording, your vowels would need to be more pure than they are in your own recording. That said, I write all this knowing that you may have
intentionally softened your sound due to using acoustic guitar rather than electric. In which case, just ignore me
Hope you don't mind this post, but I figured I'd give you some feedback since it was something you did for an audition. When it comes down to it, your renditions are very good, so you shouldn't feel like I'm saying they're not by any means
Congrats on the new job, sounds like a great opportunity