@canned_f3tus At the moment I would recommend the Emperor over the Exorcist, as the Emperor is the better combat vessel if you disregard the carrier capabilities. But, if the Heavy carriers become useful again, it's more or less a 50/50 depending on what you want: better hp and firepower or better battlefield flexibility (due to the better speed and mobility on the GC), usually the latter is more useful, especially since the Exorcist costs less but that's just my opinion.
Vengeance is a good alternative in PvE to the Overlord if you want something a little bit tougher with better broadsides, but it will never be as competitive in PvP since it lacks the Ramming Spur and Torps which allow the Overlord to do massive alpha strikes that the Vengeance can't match.
Avenger is cheesy in 2v2, the low price makes it very abusable in that format. The damage and hp for that price is also off the charts for the amount of value you get, but everywhere except 2v2 (and PvE, I guess); the low range, poor speed and mobility and average accuracy for a ship of that weight class makes it a very poor choice. The lack of Prow or Dorsal weapons, which hurts most GC's playablity, also really hurt the Avenger particularly harshly for those reasons.
Executor is kind of like the Chaos Avenger, but worse in almost every way. The lances just don't hit hard enough or crit often enough to put it on par with it's IN competitor. Otherwise, same applies here as to the Avenger, particularly bad in a fleet which has almost no synergy with such a play-style (with the exception of some wacky brawling builds). Never run it, play the Acheron instead if you want lances.
Retaliator suffers heavily from a lack of weapon synergy, high cost and the fact it's carrier capacity is now practically useless. It looks particularly bad in the Chaos line up, when you could take the Styx for cheaper (with better weapon synergy), or the Despoiler which has massively superior weapons for a carrier in terms of both value and weapon synergy (the additional toughness doesn't hurt either, you literally only sacrifice turn rate and emergency turns). The main issue with its Macro weapons it has is that they are short range, and most Chaos ships don't want to be in short range, so either you build your whole fleet as a close-in brawling fleet (and the Retaliator's prohibitive cost will hinder such fleets severely) or this ship is going to get isolated and destroyed in no time. Don't use it, it's the worst of the Chaos Heavy carriers.
Repulsive is probably the only Chaos GC worth considering, cos it actually corrects the problems most GCs have. It has dorsal lances, so isn't totally useless if you're chasing down a kiting enemy, and has torps which can be brutal in close quarters. It's DPS is decent for the weight class, it's got respectable range, It's decently tanky and gives you a good alternative to a heavy brawler (since the Chaos lineup lacks of BB that fills that role, and their BCs are also generally poorly suited to the role as well). Compared to the other two, it's a like a breath of fresh air. Consider maybe taking one if you're feeling experimental, but beware, it is slower than most Chaos ships and that may restrict your battle-plan in some match-ups; so it's certainly not an auto-pick.