I mean, it was certainly more amibitious than either of them, and those two were plenty ambitious as it is. Where Tatami and Ping Pong were both highly eccentric coming-of-age stories, Kaiba is a highly eccentric dystopian high-concept sci-fi, revolving around the concept of a fictional universe in which memories are tangible, modifiable, and transferrable.
The first thing you'll notice about Kaiba is that it is visually stunning. This extends far past the surrealistically cutesy character designs and bizarre environments - the animation is tremendously fluid, the visual design is a thing of awe, and the impressive and elaborate set-pieces are a great example of Masaaki's incredible talent as a director.
The design isn't just a shallow aesthetic choice, either. The cutesy designs are a stark contrast to the dystopian setting, making the graphic nature of this series far more unsettling than it would have been given a more conventional presentation. The music is similar, in that it is a mix of creepiness and childlike innocence. The bizarre technology is a great part of Kaiba's aesthetic as well, with the vehicles, weaponry, and memory technology bearing a creative design that comes off as both high-conccept and cutesy at once.
The early episodes are the series' strongest, each of them an episodic vignette about the planet the episode is set on. These build excellent short stories that not only make for great worldbuilding, fleshing out a well-realized setting in which human lives are cheap and where memories are a commodity, but also create the kind of ethereal, atmospheric dreamscapes out of the setting that you can really lose yourself in.
The problem with Kaiba arises when it becomes plot-driven in the latter half. While the core of it - a central character conflict between our three leads, Kaiba, Neiro, and Poppo - is very strong, it gets lost in a larger entanglement of numerous subplots revolving around minor characters that become impressively convoluted in a short span of time. There are an absurd number of twists regarding the identities and goals of characters before the plot even has time to make us invested in them. The viewer never has a chance to be grounded in what they are supposed to believe - it's hard to be surprised by a twist about a character you never knew from the start, and harder yet to understand why any character does what they do when their supposed motives and alliegiances will shift at the drop of a hat.
But for a series with such a poorly-executed plot (and do keep in mind, this would be the death of almost any lesser series), Kaiba remains a remarkably impressive piece of work. The concept is brilliantly utilized, the setting is both engaging and entrancing, and the presentation is damn near peerless - perhaps rivalled only by Masaaki's later work. There's also some surprisingly strong characterisation in play here... not for the titular character, though, who is mostly a blank slate (which, to be fair, is used to great effect in the early episodes), but for Poppo, who is perhaps the only good example of a shift in motives in this series (and there are many). To elaborate too much on this would be to ruin it, but I will say that there's a certain scene in his backstory that evolves as the plot progresses, and this is combined with certain plot devices in a clever way that shows Masaaki's directing as nothing short of masterful.
Final Words: Kaiba really is a unique, impressive series, and I'd highly recommend it. But it is frustrating that it didn't live up to its full potential - perhaps if it were longer, it would have been able to fully flesh out its plot.
Story/Plot: 4/10
Characters: 7/10
Animation/Art: 10/10
Music: 10/10
Acting: 8/10
Overall: 8/10
For Fans Of: Angel's Egg, The Tatami Galaxy
