Air‑flow/Heating design: Horizontal (fan at back) gives even drying with minimal tray rotation; vertical (stacked trays) is more compact and affordable but may need you to rotate trays. 

Temperature control & timer: Adjustable temperature is important (especially for jerky or thicker foods). A timer or auto‑shutoff adds convenience. 

Number & type of trays: More trays = higher capacity. Also look for mesh or fruit leather sheets if you’ll dehydrate small pieces or purees.

Build quality & materials: Stainless steel or food‑safe plastics are preferable. Trays should be sturdy and ideally dishwasher safe. 

Energy use, noise & cleaning: Machines will generate heat and may run several hours — check wattage and how noisy/ventilated it is.