In a surprising bit of good luck, my Black 32GB Nexus 5 arrived yesterday. Originally scheduled to ship on November 27, I'm still just shocked and delighted.
Given that it arrived at 8:35 AM, I decided to take the day off to put it through my normal checklist of tests I perform on all my new phones. Once those were done and passed with flying colors I decided to perform a side by side comparison of build quality, displays and button operation compared to my very enjoyable, fast and trouble free Galaxy S4.
I found these two far more similar and excellent in the categories mentioned than originally anticipated. For my personal tastes I find each of the two displays absolutely stellar. They are simply _different_ just as I expected. Unlike many people, I do not find exaggerated or unpleasant colors present in the S4, they are just different like the two manufacturers that build these phones. In fact, they're so close to being the same I honestly have no preference, nor do I find one "the winner".
That said I do prefer the stock "Pure Android" experience much to my liking, it's the influencing factor that caused me to buy a Nexus 5, despite the fact I am very happy with my S4. One taste of pure Android, as provided months ago by my 2013 Nexus 7 and I was convinced that it was a must have for me as soon as I could obtain a Nexus 5.
Either way, S4 or N5, you cannot go wrong, this is a perfect example of relying on your personal preferences to be your guide. Hopefully I've given you another useful viewpoint for your consideration.