Well, after looking over the Black Templar Rules, now its time to start on their codex entries! And where better to start than with the HQs? (This post will be relatively short, but it covers alot in that shortness!)
First off, We'll look at the Emperor's Champion, as he must be included in any army over 750 points.
First off, we notice that he is the only thing in the codex that is WS 6. This gives him an edge in combat over the other HQs. Plus, the fact that he already has artificer armor, an iron halo, terminator honors, crusader seals, frag grenades and a bolt pistol, along with an awesome weapon in the Black Sword, makes him the cheapest HQ with that wargear you can take.(This includes the price of any vow you take with him!)
However, there are a few bad things about him. First off, he's only BS4, while all the other HQs are BS5 (I know, he only has a bolt pistol, but every bit counts). For a warrior who is supposed to be great in CC, only coming with 2 Attacks in his profile (Terminator Honors included) is not a good thing for him. I'd expect him to at least have 3.
However, any cons to the Emperor's Champion are usually placed aside due to what you get for his price. For an HQ that is at a max 140 points, you get a lot more than you pay for! The only problem that comes in is when you want to use another HQ choice, the points spent in HQ start to rack up rather quickly.