X1's buster is my definite favorite. That being said, boss Damage Barrier mechanics bit it in the ass. If the X1 buster existed with X2's physics, it'd rock all.
Yes, X1's enhanced buster does only normal charged-shot damage. However, two things can potentially screw you in addition to that. One is the hang-time that allows the exceptionally quick-thumbed for fire an uncharged shot ahead of the spread, thus doing minimal damage to a boss and the Damage Barrier blocking the charged shot. The other is the fact that at point-blank the shockwave from the buster hits in addition to the spread. This little trick is what lets you wipe out Mega Tortoise in a single shot, but against bosses, it does minimal damage and activates their Damage Barrier, blocking the spread completely.
Think of it as the polar opposite of Gaia Armor's shot (worthless against enemies but absolutely rapes against bosses).
Anyways, to the original topic at hand:
Best Armor: Gotta go with X1. I can't say no to my favorite buster. But I'll give a runner-up to Shadow Armor. Equip Ultimate Buster, Overdrive, and Hyper Dash, and the thing is unstoppable.
Worst Armor: Blade Armor. X3's buster may have been absolute suck, but at least it had a double-air-dash and added a Z-Saber wave (yes, that's an armor ability; X gets only a close-range blade unarmored). Blade has an equally crappy buster and considerably less redeeming points. It looks cool, and the concept was cool, but the thing simply lacks power all-around. Even the Giga Attack is weak.
I have a long list of favorites to give honorable mentions to, though.
Falcon Armor - One of X5's few redeeming points, give it Speedster and you can REALLY fly.
Gaia Armor - Crippled by the game design, the buster would EASILY be worth the slowed dash if death-ray-hell wasn't the first stage you visit after completing it. The insta-charge absolutely destroys bosses.
X-Fire - Kickass design overall.
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