The convenience of a slow cooker's set-it-and-forget-it is appealing, but I'm on team cook-it-fast in a pressure cooker.
Kenji Lopez-Alt has an interesting feature Why Anything Slow Cookers Can Do, Others Can Do Better
The science of how these appliances cook is fascinating: A Dutch oven with its lid cracked, placed in a 225°F oven, will reach equilibrium at around 180 to 190°F—hot enough to produce a few lazy bubbles, but not a rolling simmer.* In a Dutch oven set in the oven, you also get pockets of heat, both right next to the edges of the pot and at the surface of the liquid. On a stovetop, a Dutch oven will get a little hotter—between 190 and 212°F, depending on how hard it's simmering. The temperature a slow cooker maintains can vary greatly from brand to brand, but I've found that in most cases, on the "low" setting, you're hitting a range that is a little bit below that of a Dutch oven in the oven. More importantly, because you are heating through a thick ceramic insert, that energy comes very gently from the bottom, and, to a very slight degree, from the sides of the pot. There are no hot spots.
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This may seem like a good thing, but in practice, it means that a slow cooker cooks, well, more slowly, and in most cases never achieves the same results as foods cooked in a Dutch oven. Vegetables remain firmer. Meat remains tougher. Dried beans do not tenderize as well, and starches and gelatin are not as activated, leading to thinner results.
By contrast, a pressure cooker at high pressure cooks at around 250°F.
He then compares his results for cooking pea soup, tomato sauce, and beef stew with these methods, and also points out that crockpots excel at keeping foods warm for serving, cooking stuffing or bread pudding, and -- carmelizing onions.
