Since their arrival, different types of air fryers have multiplied on the market. Double-basket models, which allow users to cook two dishes at once, are divided into two families: vertical ones, with stacked baskets, and horizontal ones, with baskets placed side by side. The material of the baskets also matters, such as Teflon, ceramic, or glass. In addition to the obvious question of space, the issue of performance also arises. In our guide to the best air fryers, you will find both types of products. The thorny issue of space is the first difference between the two formats. A vertical double-basket air fryer is much better suited to smaller kitchens, especially in urban housing. For example, a horizontal model such as the Ninja CRISPI DualZone measures 42 centimeters in width, which occupies a large part of a narrow countertop. For comparison, the Philips Vertical Duo Série 4000 measures only 23 centimeters in width, which is better suited to a small kitchen. This slimness, however, has a drawback: depth and height. As you can see, the Philips air fryer is much deeper than the Ninja, with almost 47 centimeters compared to less than 30 centimeters for the CRISPI DualZone. These air fryers are also taller: check that they would fit if you have high kitchen cabinets. Vertical air fryers also raise the issue of heat dissipation. Whether it is the Philips or even the Cosori Turbo Tower Pro Smart, the heat dissipation occurs through one side or through the back. Therefore, you need to arrange a dedicated space in your installation. The heat: two different philosophies. On vertical air fryers, the hot air comes from the top of each basket, as with horizontal models. However, it is recommended to shake the baskets during cooking, because their low height forces you to stack the food. The cooking time also increases for certain foods, such as potatoes. To avoid this, fill the baskets less. On horizontal models, the higher baskets allow for more uniform cooking. Another limitation, the vertical air fryers can accommodate less voluminous foods. On the Philips Vertical Duo, each basket offers about 9.5 centimeters of useful height: a whole chicken or a large roast will not fit. On some horizontal machines, the containers are of different sizes, which allows you to prioritize a large piece on one side and the filling on the other. Ceramic or glass: which material to choose? Another question arises at the level of the basket material. Most air fryers at the beginning of the commercialization had ceramic baskets that cover an aluminum base. Some manufacturers, such as Ninja, now choose glass containers. The material also matters in terms of health. Ninja presents its glass containers as PFAS and PTFE-free, the component of Teflon. On a coated basket, be sure to check the "PFAS-free" mention on the product sheet. The ceramic coating has the advantage of heating very quickly. It is also a so-called "inert" material, meaning it does not chemically react with its environment and remains stable, regardless of the conditions it is subjected to. Even at 230°C, it does not emit any toxic steam. It is also naturally non-stick. However, the heat can sometimes be too intense and burn the food. Another drawback, the basket is opaque: you have to open the drawer to check the cooking. Philips circumvents the problem with a window on each basket of its Vertical Duo. Ceramic can be found on both entry-level air fryers and more expensive models, such as the Philips Vertical Duo at 249.99 €. On the cheaper models, the coating can be damaged over time with cooking and washing, especially with a metal utensil or an abrasive sponge. In comparison, glass is a material that heats much more slowly. However, once it reaches the right temperature, it allows for more homogeneous cooking. Moreover, the transparency of glass allows you to check the cooking without interrupting it. Glass is also more expensive. The Ninja CRISPI DualZone, launched in France on September 16, 2026, is sold for 329.99 €, while classic double-basket air fryers usually range around 200 €.