Nephilim Jetfighter

The Nephilim Jetfighter is the Dark Angels' air superiority fighter. It is flown by the Ravenwing to allow their ground-bound battle-brothers to focus on catching Fallen Angels SHOWING THEIR DEVOTION TO THE EMPEROR without having to worry about getting attacked from the air.

The Jetfighter was added to the Dark Angels' Codex in 6th edition to help set them apart from the other Chapters of Space Marines that get their own codices. The lore justification is that the Dark Angels had the Jetfighters for longer, but only recently found the STC pattern of a superior engine that made them practical to use (though given that the Nephilim is neither Supersonic nor Fast, the previous engine must have been really bad to force the Dark Angels to keep them grounded).

Nephilim Jetfighters pack a twin-linked set of heavy bolters and six "blacksword" missiles (36" S6 AP4, named because of their black smoke trail -- which is a lot more sensible than the Blood Angels' "bloodstrike" missiles), with a choice of twin-linked lascannons or an Avenger mega bolter in the nose. Not the most difficult of choices.

This fighter is excellent proof that if the different organizations of the Imperium would learn to share and not be selfish assholes, the Long War would be Long Over by now. Seriously, the Dark Angels use this thing to mow down every enemy air craft, even Eldar (the ones who get 40-1 kill-death ratios against Lightnings). Do they share this with the Guard? Hell no! They don't even share it with other Space Marines. The jerkasses could at least give the Guard and the Navy the data for making damn blacksword missiles. Screw the Mechanicus, they have enough toys to dickslap. Besides, if they got it no one would hear of it again for a few centuries, if ever.

Dark Talon

A variant of the Nephilim, in the same way a Darkshroud is a variant of the Land Speeder (both are rocking the "Bolt a bunch of kickass masonry to the hulls" look). But unlike the Darkshroud, the Dark Talon has no idea what it wants to do with its life, at least on paper.

It's got a Rift Cannon, two Hurricane Bolters, a Stasis Bomb; all relatively low strength and poor AP weapons. It also has the Hover Strike special rule meaning it gets Strafing Run, but only if the flyer decides not to move in the movement phase, so one could be forgiven for thinking the Dark Talon is the anti-infantry to the Nephilim's anti-vehicle.

But you can't drop a bomb while Hover Striking, and the Stasis Bomb is designed to debuff rather than kill so your Deathwing Knights can troll with impunity. Same goes for the Rift Cannon to a lesser extent. Its guns are also pretty short-ranged, making it tough to hit things in Zoom mode and running the risk of your templates scattering onto your own troops.

Tabletop Analysis

The Nephilim and Dark Talon are rather unpopular choices for a Dark Angels army, but their weaknesses have kinda been blown out of proportion. They're not bad, they're just overpriced for what they can bring.

Both flyers suffered the sin of being the second "true" flyers out of the gate in the 6th Edition: The Heldrake that preceded it was rapetastically awesome (until the 7th ed FAQ) showing that the design team were still trying to figure out how these newfangled rules work.

It was only after "Death from the Skies" came out that pre-existing Storm-talons/ravens became proper flyers as opposed to fast skimmers and they already had enough firepower to get by in the 6th edition environment, they only really needed (and received) the "flyer" rule to be added to them.

The Nephilim is great against skimmers and other light tanks, but an 180 point investment that can't kill AV14 and takes three or four turns to kill AV12 is just too iffy for most players. That's only 20 points less than a Stormraven with the same lascannon + heavy bolter loadout. But the raven has far better missiles, +1 AV all round, ceramite plating, power of the machine spirit also has a transport capacity and can carry dreadnoughts

For 180 pts you have the option for either an avenger mega-bolter or las cannon. However you can't replace the heavy bolter with anything more useful. So if you try to take

As for the Dark Talon, it's far harder to directly compare to any other flyer since nothing else performs a similar role. Dropping your opponent's Initiative and Weapon Skill by 3 is always hilarious, doubly so when you drop a Blind test on his snipers immediately afterwards, but for 160 points the fact it has only one bomb and the lack of AP isn't doing it any favors.

Alternate take: God damn does this thing sucks. A twin-linked heavy-bolter with either a twin-linked las cannon, a buffed assault cannon, and four regular assault cannon strength missile shots. For 180 pts. Its incapable of any serious anti-armor role with only one las cannon, and four, limited use, assault cannon shots. Anti-infantry is a better role for it but between the Black Knights and Deathwing Knights they already have that covered. And with no other anti-air most DA players will be looking at it for turkey hunting, its weaker build, instead. The heavy bolter is also something of a crutch, with no way to replace it for something more useful at all. Its okay in the infantry build, but utterly useless if you intend to do anti-armor.