@Eyegore,the main difference between the systems is that, while in X-Wing, you plan your move every turn, in Armada, you might be planning moves 3 turns in advance for the larger ships. Regarding play time, even though Armada is limited to 6 turns, it generally takes around 2 to 2.5 hours for a full 400 point game, so it is more suited for someone who has a lot of free time. As for learning curve, it is a steeper curve than X-Wing, as there are some ships, the Neb-b and the Raider, that are very difficult to fly well. And in regards to cost, after the 100 dollar buy in, the expansion's are much more reasonably priced.
Sorry for the wall of text, mobile isn't the best platform for posting.