Both Ohnogi, Hiroshi (Script) and Akane, Kazuki (Director) worked on these series. The stories are epic and have a futuristic feel to them. More Tetsuwan than Noein, though. You'll notice that the same animation style was used in both of these series' fight scenes from time to time as well. Escaflowne is also another done by those two.
Action, love and time jumping - what more could you want? Both these anime have epic love stories that cross time and space which of course involves actually jumping through time and space. Both have a fair amount of action, but still have a coherent plot - always nice. They also have a similar visual style, but Birdy luckily does not have the tacky CG effects like Noein.
Animes dealing with the present being influenced by societies with more advanced technology. In terms of human relations they are both relatable despite the incomprehensible settings, and deal with dark sides of the mind. I can honestly say I was deeply touched by the characters and at the same time tremendously excited by the stories and their unforeseeable plot-twists and turns. If you are willing to sit through the first season of Tetsuwan Birdy Decode, which is undoubtedly not as good as its sequel, chances are good you will not regret it, and likely quite the opposite.
Director Kazuki Akane seems to have a pool of themes (and a pool of voice actors) he enjoys returning to, except he puts a slightly different spin on the themes each time they crop up. Birdy and HGJ had similar feels from the start: both featured an eccentric pair trying to track down criminals and bring them to justice, and the style of the dialogue felt similar as well, due to longtime Akane collaborator Hiroshi Ohnogi working on the scripts. In the second season of Birdy, however, the similarities multiplied -- voice actors were even brought back from HGJ to play similar roles on Birdy. While both shows stand perfectly well on their own, it's interesting to see the same themes explored in different fashions on both. Fans of the style of one show should get a kick out of seeing a similar style in the other show, especially as it's a feel not often replicated in anime: what matters most in an Akane show is what ISN'T said, and both HGJ and Birdy are excellent examples of this. read more
The two series follow the actions (and possibly the effects) on terrorism.
Plot wise, both have a detective/ investigator that hunts down terrorists/criminals in the city of Tokyo. It follows a somewhat mystery that gets expounded within each passing episode. In addition, it explores the past of the characters, following themes of law and order.
However, Zankyou no Terror seems a bit superficial with the usage of mythology and thriller, despite the very realistic setting and art style. On the other hand, Tetsuwan Birdy Decode:02 has a much more character driven plot and is surprisingly more human despite the heavy action scenes, the sci fi setting (though mostly takes place in Tokyo), and the large cast of aliens.
Also, both have made blatant uses of historical events for their fictional universe. If you have seen either one, you'll obviously know what I mean. read more
A somewhat sexualized female police officer with an abnormal strength as the lead. The exploration of her past and her nickname. A radical terrorist group. The focus of millions of refugees living from the destruction of its fictional universe.
Despite the similar premise, the tone and execution is quite different. Tetsuwan Birdy Decode:02 uses its broader political structure as a springboard for its cosmopolitan characters. Focusing more on its dramatic past, it pushes aside a lot of the political intrigue unlike GitS. It also has a much more wider spectrum of tones and genres and is more cathartic with its set of characters.
Meanwhile GitS SAC has a more regimented set of characters and a much more thicker political climate with a more solid establishment for its setting.
I would recommend the preference for either a space opera or a cyberpunk anime. Still, both are pretty good sci-fi ,action, drama.  read more
While Birdy lacks some of the epic-ness of TTGL, they are similar in many respects. Both successfully incorporate action into a meaningful and interesting plot, both question the the meaning of humanity, and both can pack an emotional punch. Additionally they both involve love, space and aliens, and I would say their visual style is similar.
Episode 87 specifically of Shippuuden features Shingo Yamashita, who does most of the action for Birdy 02, as well as other key animation scenes. If you enjoy his fight animation, you should check out his other stuff.
Both made by A-1 Pictures, they feature a similar type of quirky, lifelike animation in their first episodes. If you enjoyed Shingo Yamashita's animation, you may want to watch his other involvements. Obviously, Birdy has more action, whilst Kannagi is more realistic.
One is a bounty hunter, the other is a federal agent, but they both hunt alien. Action packed series with old school vibes, strong SF pulp influences, groovy soundtrack and really stylish animation. Significant efforts have been put in these two underrated gems.
While the first season of Birdy Decode is a bit chunky and awkward like the first half of Lost Universe, the second halves shine with gripping stories featuring tragic pasts and themes of revenge with characters grown mature and sympathetic.
Both are stellar action anime featuring simple if likable characters in a suspenseful cat-and-mouse game. Birdy's second season has her hunt down a group of bad guys who've gone into hiding while Towa no Quon's conflict centers around a group of heroes trying to elude a shady organization. What's nice is that the protagonists in both are skilled fighters who are nonetheless far from invincible, which gives the action sequences some actual tension.