At the present time I own three stainless steel Presto pressure cookers..4, 5, & 8 qt capacity.
If you are not familiar with pressure cookers, you need to know this important information: The stated capacity of the cooker is to the brim of the pot. However, because of the need to generate steam in order to cook under pressure, and to prevent steam-born foods from interfering with the pressure regulator and safety features, food should never exceed the 3/4 full level, and in some cases, not more than 1/2 full. Foods that foam, such as beans, rice, chicken, to name a few, are in the latter catagory. And some are not recommeded at all for pressure cooking, (although there is a way around that).
Therefore, if a pressure cooker is rated with an 8qt capacity, the most you can ever cook under pressure would be 6 quarts.
As for types, as I said, I have Presto cookers. This is because I am of a practical mind, and want the most for my money while still getting quality. However, there are now on the market, pressure cookers called "new generation" cookers. Instead of the traditional 'jiggler' type weighted pressure regulator, the pressure in these is controlled by a spring-loaded pressure regulator. They are regarded as 'easier to use'. All pressure cookers on the market today are equipped with multiple safety features, so even the 'budget' ones pose no danger, if used correctly. 8qt is the largest stainless cooker produced by Presto, although they do produce larger aluminum pressure appliance for home canning. You may find larger stainless PC's from Fagor or Kuhn-Rikon, although you may be hard-pressed to find any stainless cookers larger than 10qt. Fagor, a Spanish company, produces fine cookers in the middle price range, and with many fine accessories. On the high end, there is the Kuhn-Rikon pressure cooker. This is the brand you see most often in use on the Iron Chef America show.
Whichever one you choose, be sure to do your homework regarding availablilty of parts and warrantee. Also ask about the maximum psi (pounds per square inch). Most pressure cooker recipe books are written for cookers with 15 psi, so with cookers with lower maximums, it becomes necessary to adjust cooking times. Some cookers do have adjustable pressure from 10 t0 15 psi. When you are researching, do not accept the sales person's say-so on any of these questions. Often they don't know, but instead of admitting it, they just say what they think you want to hear. With internet and toll-free numbers, you can go directly to the source for your information. I hope this has been of some help?
If you need a really good referrence resource and recipe book, check out Miss Vickie's Big Book of Pressure Cooker Recipes, by Vickie Smith. She also has a website where you can get many of your questions answered. :lips:
PS DO NOT purchase a pressure cooker with the intention of using it also for home canning. Canning is a whole other science, requiring specific equipment, and accurate timing. Unfortunately, some retailers continue to market pressure cookers as dual function appliances, advertising that they can also be used for canning.
update: I looked at the Kuhn-Rikon website. They do offer a "12 qt (actual capacity for pressure cooking=9 qt max) stainless family stockpot" for $450. I have no doubt that it's worth every penny. Here is my opinion: This would be a life-time investment (providing the gaskets will always be available). However, unless you know that you will be using this size cooker at least once a week, you might consider purchasing two 8 qt cookers instead. Then, for large batch cooking, use them both.
Expect to see that some of these pressure cookers have been outsourced to China, or some other country. Even so, they still must meet the safety standards set by the USDA.
"The pressure's on...let's cook something!"