if my memory is correct this dlc are cosmetic or get some weapons :

Firepower Pack.
Aegis Pack.
Equalizer Pack.
Alternative Pack 1 & 2. 

but the other :

Arrival.

Lair Of The Shadow Broker.
Kasumi Stolen Memory.
Overlord

each have  a questline with a impact for mass effect 3 

if my memory is correct this dlc are cosmetic or get some weapons :

 

 

Firepower Pack.

Aegis Pack.

Equalizer Pack.

Alternative Pack 1 & 2. 

 

but the other :

Arrival.

Lair Of The Shadow Broker.

Kasumi Stolen Memory.

Overlord

 

each have  a questline with a impact for mass effect 3 

Yep exactly what you say.

Get Shadow Broker if you can buy it for less than 10$. The rest is not worth the price.