Electric or stovetop? Stovetop cookers reach a higher pressure, reach it faster, and maintain it longer than electric models, and they're more compact for the volume they hold. Electric models are more versatile -- often doubling as rice cookers, slow cookers or both -- and may be easier for owners new to pressure cooking or those without enough stovetop burners when cooking a multi-course meal.
How many are you cooking for? For a small-to-medium-sized family, 6- or 8-quart pressure cookers are best, while a 4-quart cooker is fine for one to two people. Canning and some super-sized recipes and cooking tasks, like preparing a whole turkey, require a much larger pressure cooker or canner, but the bulky size makes it more challenging to store or use regularly.
What kind of cooktop do you have? Many pressure cooker and pressure canner manufacturers don't recommend using a pressure cooker on a smoothtop, or glass or ceramic stovetop. Smaller pressure cookers should be okay, but you have to take precautions not to slide the cooker on the cooktop (which is true of any cookware you use on a glass cooktop). In addition, some glass cooktops struggle to get hot enough to get a pressure cooker up to its highest temperature. If you have a glass or ceramic cooktop, you'll probably be better off with an electric pressure cooker.
How much space do you have? Most stovetop pressure cookers are about the same size as a large pot, but the domed lid with handle make them a lot taller, so you'll need to be sure they fit on the shelf where you intend to store it, although some experts say you should store pressure cookers with the lid off just in case there is any residual moisture. Electric pressure cookers are big and bulky; if you want to keep it on the countertop be sure you have the space to do so. You should also measure the clearance above your range before purchasing a larger capacity pressure cooker or canner.
The one consistent comment we saw across the board about all types of pressure cookers is that the included recipe books and/or instruction books are really, really bad. Often, cook times are confusing, or it's not clear exactly what cut of meat they are referring to, or they seem to be written by someone whose first language is definitely not English. Be patient and turn to the Internet. There are many excellent web sites and videos that will help you figure out how to use any type of pressure cooker you have. For example, HipPressureCooking.com has a handy chart to help you determine pressure cooking times and liquid needed for practically any food. And you do need liquid -- pressure cookers are not meant to be used dry and may not work if you try to do so. There are also a number of cookbooks dedicated to pressure cooking, and they have saved the day for many a bewildered new pressure cooker owner. Don't be afraid to experiment and put the food back in to cook longer if it's not quite done. Eventually, you'll get the hang of it and be pressure cooking like a pro.