After that monster of an entry for HQs, Elites should be fairly straightforward, yes?
In most armies, the Elites section is where you'll find the heavy hitters, the go to units, the MVPs of the Codices. Stuff like Terminators, Fire Dragons, Lootas, and Hive Guard. These are the units that give your army teeth. Also you'll find Legion of the Damned, Mandrakes, Ogryns, and Stealth Suits. Utter shit. For better or worse, your Elites choices can make or break you.
It's no different with Daemons. Though they only have a paltry 4 to choose from, they run the full gamut from holyshitthisisawesome good to whathefuckisthisIwantmymoneyback bad.
S5, T5, 2 wounds, 3 attacks, 3+/5++, power weapons, wound allocation shenanigans, all for 40 points? Sounds too good to be true. It is. Bloodcrushers look great on paper, they're the durable and hard hitting unit Daemons sorely lack. The catch? They move like infantry. That's right, giant metal daemon rhinosauruses with fire for blood can't catch up to a damn METAL BAWKS. For all the hype, Bloodcrushers just don't have the mobility necessary to be effective assault troops. They would make for good area denial to protect your shooting units that can de-mech the enemy, oh wait, Daemons don't have that either. Dropping multiple small units as well as Kheralds on chariots and foot DPs could cast a fairly wide net, but to what end? In truth, they only excel at one thing: murdering slow infantry. In the land of mech, jump packs, bikers, and variable deployments, who puts a bunch of dudes on foot? Noobs. Say hello to the Noobcrusher, scourge of the marine gunline. I desperately want Bloodcrushers to be good, the models are fucking sweet, but they just fail.
Flying super Horrors with upped BS and Breath of Chaos. They can make for a mobile and versatile shooting unit if you add in Bolt of Tzeentch, capable of handling infantry up close, at medium range, or pop a tank should the need arise. They get a lot of use as suicide units, but that isn't very feasible. First, they have to drop in flamer range on an enemy on foot (how did they get on foot, you certainly can't pop their transports, more noobslaying!), risking scatter. To mitigate scatter, you bring an icon (so the enemy unit on foot not only has to be on foot, but also stay there for a turn within flamer range of an icon, the hell?), but it doesn't always work out nicely. I prefer them as a mobile reserve as I alluded to before. Still, for all that, they are fairly pricey and very fragile. If you can gun down T4 4++ you can gun down Flamers, one of the other big problems with the suicide unit. Drop in out of sight and use that flight to get where you want to be while staying safe. People use them poorly, but I think they have a use if you want some fast and versatile shooting.
Well, let's see. T4, 2 wounds, 5++, no grenades. It's ok I guess. Wait a minute. S5? I5? 5 attacks?! Rending?! Beasts?! Hit and Run?! 30 fucking points?! Ho Lee Shit. I can stop the review here, Fiends win the slot. Cheap cav that can and and will catch up to anything (their own movement plus Slaanesh's Ping Pong Ball trick as detailed in the Keeper of Secrets entry gives them an effective threat radius of 24" before assault and 42" after) and stand a good chance of tearing it to pieces. Fiends are your answer to mech, as most vehicles are AV10 on the rear and they can easily catch up to it and rip it apart through sheer number of attacks. Fiends are your answer to mobile enemies, catching them with their natural speed and killing them, tying them up, or weakening them for your punchier stuff. They are your answer to shooting, quickly catching and killing, weakening or tying them down. With S5 and rending, they can kill anything from Guardsmen to Godfexes and threaten any armor value up to 14 (improved if you give on Unholy Might). They do have weaknesses, the aforementioned average T, low save, and no grenades, but their low cost and ridiculous speed/hitting power make up for it. Get 18 now, all the time. If you aren't maxing on Fiends, you had better have something cool in mind or I will slap you silly. Fiends fucking rule.
Beasts of Nrgle
Talk about ending on a sour note, I told you I should have ended it at Fiends. Beasts of Nurgle suck, unequivocally so. They are tough and can potentially dish out a lot of poisoned (2+) attacks, but S&P ensures they never see combat, their cost (more than Fiends!) ensures they'll never be taken over any of the better Elites, and the existence of Fiends ensures they'll never be worth mention. Worthless sacks of shit, and also their rules are terrible.
So, that's the Elites section. I figured that with only 4 choices I had better go into more detail, so it still ended up long winded and meandering. Suck it brevity.