It's amazing how much of a difference a little time (and a different production studio) can make in the look of an anime. When "Full Metal Panic!" was released in 2002 by Studio Gonzo, it was in 4:3 format, clearly making experimental use in the yet-imperfect blend of 3D animation and 2D "digipaint" animation. Even compared to other shows of that year, "Panic!" season 1 did not look great then, and has aged even worse, a sad detriment to what was otherwise a solid (if still imperfect) action/comedy show. A proper second season, called "The Second Raid," was released in 2005 (we'll ignore the in-between comedy spin-off for now). Only three years later, and with a different production studio in Kyoto Animation (and a different director in Yasuhiro Takemoto), and the series looks completely different. It's in proper 16:9 aspect ratio, and animated at close-to-HD (not quite 1080p, but still pretty good), with little use of distracting 3D animation. The difference is stark, and "The Second Raid" still looks great today; surely, this is how "Full Metal Panic!" was meant to look from the start.Kyoto Animation today (this writing is in 2019) is famously one of the top television anime studios, known for their high quality in digital 2D animation. But this show was released before their big financial successes, "The Melancholy of Haruhi Suzumiya" and "Clannad," so that they were able to keep such a high level of animation output early in their existance ("The Second Raid" was only their fourth show, according to Wikipedia) is impressive. Animation is most impressive during action scenes, where well-choreographed hand-drawn mech suits battle in the middle of explosions, but even character animation is generally strong. The only major critique of the animation is that some quick movement feels like it was sped-up, appearing at an artificially-higher frame-rate, temporarily feeling cheap. Also, a couple episodes near the end of the series contain less action, and like many other shows, feels like a temporary dip in quality from the starting and ending episodes. Also, while there is more detail here than the first season, the visual design of the show feels a bit restricted to match the design of existing material, so character designs in particular are already a bit dated. Nonetheless, fans of animation will enjoy watching this action thriller.The story is a slightly different affair. The first season of "Full Metal Panic!" juggled genres of political-thriller, action, sci-fi, and romantic high-school comedy. It never really blended them well, often settling on separate episodes entirely dedicated to school comedy, bookending a few episodes of serious spy action for each arc. "The Second Raid" spends its 13 episodes on a single larger story, almost entirely a serious action thriller, almost entirely ignoring the comedy roots. Even Kaname Chidori, the blue-haired high school poster girl, doesn't really get a part to play until the second half of the season, and even then, the secrets of her identity feel less important than they did at any moment of the first season. Depending on your opinion to the first season, this might be a disappointment. If the espionage-action was the part you enjoyed, this might be an improvement, as it virtually drops trying to juggle an extra genre. Newcomers to the series should also be able to follow along, although there are several brief flashbacks (often with seconds of re-animated footage from the first season) that might make significance of a scene or character lost on a new viewer. The story is about "Mithril" (the secret "good-guy" organization) and it's fight against "Amalgam" (the now-known name of the secret "bad-guy" organization). In particular, Amalgam seems to be led by a mentally-unstable balding madman, and they have access to mech suits powered by the Lambda Driver technology, similar to soldier Sosuke Sagura's own suit, the Arbalest. With the original creator of the Lambda A.I. dead, Mithril has to rely solely on Sosuke to hold their own against Amalgam. Additional plot points include pair of young female Chinese twins, working for Amalgam as well-trained assassins, but with their own agenda to carry out the wishes of their "sensei," who slowly dies in their apartment. And finally, control to protect Chidori is given to another division, leaving Sosuke at odds with himself to leave her to follow orders, at a time when Chidori might be at her most vulnerable. 
This is a much more serious story, filled with more explicit violence (and nudity) than the first season. Some of it might be an excuse to get more attention (other than just for style, do we NEED to watch the Chinese twins showering together?). Some carryover elements from the first season made my eyes roll (WHAT DO YOU MEAN GAURON STILL ISN'T DEAD?!?). And I admit, for all its faults, the first season did have a few standout moments of classic scenes that came out perfectly in their writing and shots, something "The Second Raid" never quite accomplishes. Despite all of that, I think "The Second Raid" is the stronger story, paying of with dramatic battles, memorable enemies, and geniune character development for Sosuke and his multiple love-interests (this is anime after all). Even moreso than the first season, I can compare "The Second Raid" to the anime "Black Lagoon" for it's action-fueled story, which is high praise, given "Lagoon" is still the benchmark many anime fans refer to. And since "The Second Raid" (2005) came BEFORE "Black Lagoon" (2006), even more credit should be due. Aside from the barrier of entry mid-way through a franchise, this series should be on every action-fan's radar.One more note about the story: it feels like it isn't finished yet. New allies and enemies are introduced, but don't get much opportuntiy to do anything, as if the show was setting up yet another season. Even Sosuke's Arbalest suit was hinted to have a dialogue-based A.I. system in the first season, but it isn't until near the end of "The Second Raid' that we get a bit of banter between it and its pilot, a major injection of personality for the series. Fans will be left hanging though, since no third season came around, requiring fans to read the light novels for any continuation... that is, until the release of the season "Invisible Victory" in 2018, about 13 years later. Anyway, the story has some weaknesses between all of its strengths. The music is similarly solid to the first season. The opening and ending themes are slightly better, but like the first season, aren't particularly memorable, unusual for an anime. The English dub is fine, and some credit should be given to keep the "international" elements in (other languages are spoken, Mandarin in particular), but enjoying the dub is more a matter of hearing familar voices carry over from the first season. Funimation's Bluray release includes "Episode 0" (a five-minute preview trailer made up mostly of the opening minutes of episode 1, with no new material), and an OVA, which provides a nice comedic break with commander Tessa and her attempt to locate her mssing stuffed animal after a druken night, appreciatively dubbed. Watching "Full Metal Panic! The Second Raid" was a pleasure, and highlights the weaknesses from the first season. Most weaknesses that still remain in the second season are residue that will always remain from tieing itself to the franchise. Otherwise, it's a great, gritty action show, and an impressive upgrade to the first season in almost every way. It might even be worth investing in the first season JUST to watch "The Second Raid." It's that good.