HQs really haven’t changed much in how you will need to equip them. If you’re going to be spending many points on them or putting them into close combat, then it becomes imperative that you have the tools to handle yourself there, but otherwise the traits are often more important.
Since Power Weapons are AP3 you will need to think about whether or not you want to be able to kill Terminators and the like. If yes, then you need a Powerfist, otherwise a Lightning Claw or less will do just fine and let you keep your high Initiative. You may think that you need a 2+ save in order to keep it against Power Weapons, but don’t bother. Powerfists will be more common than before and a 3+ Invulnerable is a better way to go.
If you expect to face challenges then Terminator Honors becomes a good purchase and if you are really decking-out your Warlord (Powerfist, Terminator Armor, Storm Shield) then you should probably also grab an Adamantine Mantle if points allow.
Commander versus Chaplain comes down to the rest of your list. If you have an assault oriented list or a particular close combat unit then the Chaplain will suit you well. Otherwise the Commander provides a very nice army-wide benefit.
In the new edition, I think that spending the 15 points for an extra wound on your Warlord (a Marshal or a Master of Sanctity) becomes much more worth it, especially if you already have an Adamantine Mantle.
As for the Warlord traits, almost all of them are only selectively useful. However, if you are taking a defensive-based Warlord, such as one leading a Terminator Squad with Heavy Weapons or sitting back with some squads, then Personal Traits are the best candidates, potentially making your Warlord scoring, have FNP when near an objective or Counter-Attack when in your deployment zone. For an aggressive Warlord either Command Traits or Personal Traits are good choices, Command being a little more suited to having several assaulting units while Personal Traits work better for a single powerful unit.
However, since the trait you get is random, make sure that you do not rely on any of them when designing your list. That’s all I have for now, but next I will be getting into Drop Pods hopefully.