A slow cooker's whole method relies on sustained low, gentle heat over hours — a genuinely different cooking chemistry than pressure cooking, not just a slower version of the same process.
Why low and slow actually works
Extended, gentle heat over many hours gradually breaks down tough connective tissue in cuts of meat that would stay chewy under quick, high-heat cooking, converting collagen into gelatin over time — the same chemistry classic braising relies on, just automated and extended over an unattended stretch of hours rather than active stovetop tending. This is also why slow cookers work well for dried beans and tough, fibrous vegetables — the extended time does the softening work that heat intensity alone can't substitute for.
Oval vs. round shape matters for what you actually cook
Round slow cookers suit soups, stews, and chili well, where the food is a liquid or semi-liquid mixture without a strong shape requirement. Oval slow cookers are better suited to larger, shaped cuts of meat — a whole chicken, a roast — since the elongated shape accommodates a longer item that wouldn't fit as well or cook as evenly curled into a round vessel. Choosing shape based on what's actually cooked most often matters more than it might seem for a purchase that otherwise looks interchangeable.
Programmable timers and automatic keep-warm modes are genuinely useful
A programmable timer that automatically switches to a low "keep warm" setting once the cooking time elapses is a real practical feature for anyone using a slow cooker for its main appeal — starting it before leaving for the day and returning many hours later. Without this feature, food left cooking on the original heat setting well past the intended time can overcook or dry out; the automatic switch to keep-warm prevents that without needing to be home to manually adjust the setting.
Insert material affects both cooking and cleanup
Most slow cookers use a removable ceramic or stoneware insert, which holds and distributes heat evenly and can usually go from the slow cooker base to the refrigerator or occasionally the oven, depending on the manufacturer's specific instructions — checking those specific compatibility claims is worth doing before assuming any insert is oven- or fridge-safe. The removable insert design also makes cleanup significantly easier than a permanently fixed cooking vessel, since it can be washed like a normal pot rather than needing to clean around a fixed heating element.
The one thing people forget
Don't lift the lid to check on food repeatedly during cooking, since a slow cooker relies on maintaining a stable internal temperature and humidity level over a long cooking time — each time the lid comes off, meaningful heat escapes, and the cooker needs real time to recover that lost heat, which can add up to a genuinely longer total cooking time than intended if the lid is lifted frequently out of curiosity.