Idea Crossroads: Noir or Epic?

[Sahariel]

I am essentially at a crossroads as to where to take the idea of bio-mechanical augmentation taking over human society, a Heaven filled with "holy" inhabitants who enthusiastically trade away their organic form to God for mechanical forms in the name of purity, and a vastly overpopulated Hell which, as a whole, obsesses over their natural forms and making deals with higher demons to gain power. What ties together the story is constantly on my mind: I want to either go with something of a tech-noir (fusion of sci-fi and noir) type story infused with supernatural elements, or more of a supernatural/science-fiction epic. Here is a rather brief and incomplete summary:

The year is 2036, and the newly elected President who's populist appeal to the American citizens and highly organized and effective campaign sealed him an election. The President, however, was murdered by what appeared to be man who possessed the wings of an angel in the Waldorf-Astoria and Towers Presidential Suite. The "angel" thrust an elaborate sword into his heart and slit his throat to ensure death, then phased through the bullet-proof windows and flew away. How the Secret Service responds (the original idea was that they withheld the tape to avoid mass panic) is to be decided on for the story.

The assassination of the President of the United States leads Nathaniel "Nate" Saenz, an FBI Special Agent in Charge with unnatural pinkish red irises and pupils hidden by specially made contacts, to a chance encounter with a succubus named Meridiana who agrees to help him in exchange for his limitless Astral Energy, the essence of human thought, emotion, and experience which fuels all magic.

The key difference between the "noir" version and the "epic" version is the conflict between Heaven and Hell: the noir version has the main characters focus on preventing an all-out war between them whereas the epic has the war occur and has the story focus on it. Another key difference is that the noir story focuses on the detective elements and have Nate's ability to manipulate electromagnetism be far more subtle whereas the epic will focus on the action/thriller elements and have Nate's powers be more akin to a superpower.

I tried to find a way to combine the two, but I am unsure how to do it or if it is even possible. Any help with deciding which would be more interesting would be appreciated. I want to do a synopsis soon but I simply cannot decide on which to go with.

PS:

Two questions, also essential to the story.

1. How should the Secret Service deal with the tapes? Realistically, would they reveal the tapes or will they withhold the information to avoid panic?

2. How should Nate and Meridiana meet? In the original idea, Nate saves Meridiana from a group of angels hunting her down. I do not like the idea and am looking for something new. Man's inhumanity towards man is going to be the key message in the story as well as how the human desire for perfection becomes the enemy of the good. Let me know if this helps or if you need more info.

[EKublai]

I may respond more completely later, but was this inspired by Deus Ex?

[Sahariel]

Deus Ex is a rather prime source of inspiration for this, as well as various other games like the Shin Megami Tensei series as well as Neil Gaiman's books.