The Figures, Compared
For many, the central appeal of toys-to-life lines isn't really the games—it's the figures. Generally speaking, each line's figures share a lot of elements in common. They generally stand about four inches high and cost around $13 apiece. However, the specifics vary considerably from there. Where applicable, figures are forwards compatible but not backwards; e.g. you can use a Disney Infinity 1.0 figure in the Infinity 3.0 game, but you can't use an Infinity 3.0 figure in the Infinity 1.0 game. Confusingly, the reverse is usually true for the game portals!
Figures in current line: 20 figures plus 20 vehicles
Legacy figures from previous versions: About 300 (including variants)
Skylanders takes the most basic approach to toy integration: You can complete the entire critical path of the adventure with the handful of figures included with the starter set, and add-on figures and vehicles unlock optional areas or provide a tactical advantage in combat. The primary concept behind Skylanders' figures is that each is affiliated with one of 10 elements. Different areas of the game possess a specific elemental affinity, and using the correct Skylander for the current area will boost your attack power, provide experience bonuses, and more.
Each figure includes a tiny amount of rewritable memory inside its base. All experience and cash you gain in combat is tied to the current Skylander, and that info is saved to the figure. So, too, is that character's progress through its skill tree, as well as any little extras you've attached to the in-game character (such as hats). This allows you to take a powered-up characte into a friend's game.
In terms of construction, Skylanders definitely features the most complex designs of all toys-to-life figures. Each Skylander incorporates both a detailed base that indicates their elemental affinity as well as fine details such as translucent plastics or weapons. The vehicle figures from SuperChargers, while useless on their own, feature moving parts and grant gameplay bonuses to the character associated with them.
Figures in current line: 37 (including pending 3.0 releases)
Legacy figures from previous versions: 59
Disney Infinity figures work almost exactly the same way as Skylanders. Their bases—which vary according to the character's original property (e.g. Guardians of the Galaxy, The Force Awakens, Tron Legacy) rather than according to an in-game elemental feature—contain a chip that allows them to interact with a portal device and save that character's development; they can reach level 20 as of Infinity 3.0.
Infinity' figurines offer the greatest variety in terms of scale. The most recent wave of figures, for example, included both Spot from The Good Dinosaur and Iron Man's Hulkbuster armor from Age of Ultron; the former is probably the tiniest Infinity figure to date, while the latter is absolutely enormous. And dense! The line doesn't offer any price variance based on the figure's size of popularity... though you can expect to pay hefty aftermarket premiums for rare figures like Boba Fett or Kingdom Hearts Mickey Mouse.
Perhaps not surprisingly, Infinity figures appear to be the best-made of all the 4" toys-to-life figures. Their designs are less complex than those of Skylanders, and deliberately so. Because Infinity brings together so many different properties, including some live-action universes, the line incorporates a unifying visual style based on the Pixar aesthetic: Clean, simple, and angular.
Figures through spring 2016: 87 (plus 100 Animal Crossing amiibo cards)
Because amiibo (generally) aren't tied to any specific game and no longer even launch in waves, all the figures are "current"—though good luck finding certain rarities. Nintendo has taken the most aggressive approach to the collector's market, producing many figures in extremely limited quantities. The immediate scarcity of some of the less popular figures at launch last year turned the product line from a mere novelty to a national obsession. ("National" in that it's much easier to find even scarce figures outside the U.S. market.)
Of all the lines, amiibo tend to be the most consistent in size and density, but they also vary the most dramatically in design. Even discounting novelty figures like the Yarn Yoshis (and the enormous Mega Yarn Yoshi), amiibo range dramatically from the minimalist Kirby and Mr. Game & Watch to the detailed and "realistic" Ganondorf and Shulk. Their construction quality is good, but they tend to feature softer plastic to make their spiky or dangly bits (wands, swords, etc.) more pliable and break-resistent. amiibo also suffer from the most "kibble"—that is, unsightly chunks of extra plastic to support the characters. The majority of the line essentially consists of 3D renditions of Smash Bros. character portraits, which are all very dramatic but not necessarily ideally suited for plastic figurines.
As with the other lines, amiibo contain a minute amount of memory to allow character stats to be saved to the figure. Frustratingly, Nintendo only included enough capacity to save info for a single game, which was fine a year ago when Smash Bros. was the only game that supported the line but seems inadequate now that the number of amiibo-friendly titles is reaching the dozens mark.
Animal Crossing: Happy Home Designer introduced a theoretically more budget-friendly variant on amiibo a few months ago with amiibo cards. These are, simply, trading cards that function like amiibo (they have a tiny NFC/memory chip sandwiched almost indistinguishably inside). While cards only currently exist for Animal Crossing characters, at $6 for a pack of six they offer a much more affordable option for games like amiibo Festival than a full set of $13 figures.
LEGO Dimensions 3.0
Figure sets through spring 2016: 37
As you'd expect, LEGO Dimensions figures don't bear much physical resemblance to other toys-to-life lines. Rather than take the form of four-inch fixed figurines, they instead come as LEGO minifigs with a special base. It's the base, not the figurine, that contains Dimensions chip data.
Being standard LEGO products, players have the flexibility to customize their minifigs however they like, though those changes obviously won't be reflected in the game. And it's possible for the game to alter a character's appearance to differ from the figure; for example, the Doctor Who playset comes with a minifig of the Twelfth Doctor, but it's possible to cycle through all 13 different Doctors within the game. As expected, the production quality of these tiny toys is quite high, and a modest amount of assembly is required (though that's part of the experience).
Both the Dimensions starter pack and the level packs come with both figures and vehicles. The vehicles can be reassembled into different configurations, and since Dimensions characters don't innately level up themselves, the vehicle forms are currently the only data the game saves to the figure base chips. Note that the vehicles are extremely small and not to scale with the characters; e.g. the Batmobile that ships with the starter pack is barely even go-kart sized compared to the figure.
Advantage: LEGO Dimensions
All toys-to-life figurines are of high quality, but they're mostly designed to sit on the shelf. Dimensions offers the greatest play value with a series of minifigs and mini-vehicles that maintain compatibility with the entire LEGO line. (The Yarn Yoshi amiibo definitely deserve a nod for charm and appeal, however.)