Altered said:
Unfortunately, Alpha Mission II's perfect-shooter feel ends right after the 2nd mission.
From mission 3 onwards, it becomes crucial to always chose the right Armor, up to a point where your chances for surviving certain spots are very narrow if you use the wrong one or, even worse, arrive with your standard laser and missiles. It's perfectly possible to beat the game without using a single Armor, but it requires mad skills and a lot of patience - battling bosses with a low-power standard shot seems to take like forever.
Which Armor you chose also depends on your playing style, personally I prefer the offensive Armors over the defensive ones (Shield, etc.), but where I go at it with full firepower, one could also activate a Shield and take out all enemy waves and installations with some sort of surgical attack.
The only flaw in the Armor system is the random appearance of the 2nd or 3rd Armor parts, sometimes you already have parts one and two of the Nuke in order to quickly kill a boss, but level 3 does not show up in the entire level, so you're doomed if you don't switch to collecting a different Armor as long as it's still possible.
Other than that, ASO II is my fave vertical shmup on Neo. It requires a bit of strategy and planning tho, and perhaps it's that what puts some ppl off. While other games like the Sonic Wings or even Ghost Pilots are way more accessible, ASO II is much deeper and more rewarding in the long run.