Pinnacle Station is 400msp. The dlc is basically combat challenges in 4 different scenarios and 3 different locations. If you loathed ME gameplay you won't like this one.
Bring Down the Sky is only 80msp. This one is story dlc and is takes place in an asteroid set for collision with the colony world of Terra Nova. It last around 2 hrs on your first playthrough. The outcome is mentioned in Mass Effect 2 and quite possibly
in Mass Effect 3 (i really hope for a conclusion of the paragon choice).
Bringing down the sky is well worth getting. As well as the story part and the fact that it introduces Batarians there are quite good rewards. If your charm or intimidate is high enough you can get a very powerful omni-tool as a reward.
Pinnacle station is OK although it can be frustrating on higher difficulties. The reward is your own apartment with some perks like a grenade and medkit refills and the ability to order powerful mods from a trader in orbit. You don't actually see this trader
though you just order the mods on a computer.