Queen of Pain Aghanim Sceptor

There was a debate on a forum regarding QoP's ASU (Aghanim Scepter Upgrade) which only reduces his cooldown and we have been seeing them in many QoP matches.

Let's compare them with the other alternatives. Hex, Orchid and BKB.

1) ASU

Grants you a shorter cooldown . This is useful if you get in the early game to mid game allowing you to easily net kills every minute. However in team fights itself it wouldn't make a huge impact due to the fact that teamfights lasts for less than 40 seconds most of the time. Its also great against split pushers such as Natures Prophet as you can just use its ultimate on creeps.

Pros

Increase ganking ability
Able to use after buy backs
Counter push against split pushers
Gives 390 HP
Easy build up (1200,1000 *3)

Cons

No increase in team fight impact.
Not as useful lategame.

Hex / Orchid

In comparison to Sceptor, Hex gives a reliable disable allowing you to prevent a hero from doing anything at all. However its expensive and only targets one
Hero. Its great against Heroes with disable you to counter gank you. Get these when there is Hero with spells you find annoying ( AM , FV) and burst down before hex/silence runs out.

BKB

The reason for getting this is when you are getting burst down instead by the enemy. Immunity for a few seconds will grant you mobility and 2 screams off without getting disabled and blink out of the fight to bottle up and go back in.

Its build up is relatively difficult (easier than hex though) and gives decent amount of HP

So the best item is determined by the situation and current amount of farm you have and most importantly the lineup you are facing.