Going first with a drop pod Space Marine army can be one of the most crippling alpha strikes in the game... Versus Eldar for example you can shoot their units with complete impunity before they can move their skimmers for the jink save or cast any psychic powers. Versus Tau for example you can blast their Riptides before they nova charge for the 3++ save. Your initial shooting phase is very powerful when you go first as your opponent cannot counter it as shown with these examples.
Going second you lose a lot of these types of advantages though so it requires a lot more thought to develop viable tactics to make them function close to the same level. Regardless a drop pod army needs a good alpha strike to beat most other armies. This series of articles will demonstrate how to maximize the drop pod army when going second... You can't count on going first most of the time and if you're lucky you'll end up going first roughly 50 percent of the time.
Going second calls for a more protracted approach to these games since you can't play with the same level of impunity.