Cheesecakes can certainly be successfully made in pressure cookers. The size cake will depend on 2 things: 1. the inside diameter of the pressure cooker, and 2. The outside diameter of the springform pan, including the locking mechanism which usually sticks out a bit beyond the rest of the pan. My 7" springform pan fits in all three of my Presto Pressure cookers, although I could easily use an 8" pan in the 8qt one. The inside diameter of my 8qt Presto is 9 & 3/8"-- not quite enough for a 9" pan. A 7" cheesecake typically would be timed 20 minutes once full pressure is reached, then remove from heat and allow pressure to drop naturally -- approx. 10 or so minutes.
Unless you are looking at aluminum pressure cookers, the 12qt models are pretty costly. However, unless you want to stack the cakes, to do 2 at a time (yes, it can be done), you can probably use 10 qt models, because the volume difference between the 10 & 12 models is upward, rather than outward. For the purpose you are considering, aluminum cookers will work very well, and cost considerably less. However, if you want to cook other foods as well, then I would suggest you get the number of cookers you want, but have one of them made of stainless steel. That way, you have one non-reactive metal cooker that you can use to prepare all sorts of foods. Presto makes inexpensive cookers with the "jiggler" pressure regulator. I actually prefer this, as I grew up with it, and it's my comfort zone. Fagor cookers are in the mid-price range, with more modern pressure control. There are others similar to them. Then, there is the Kuhn-Rikon. Touted as the 'Mercedes' of pressure cookers, they are well-made, and some say they perform better than any other pressure cookers on the market today. Expensive, though, but if you consider it a lifetime investment, it will probably be the last pressure cooker you'll ever buy. It's a cooker you can proudly leave on the stove to show off with. (My personal opinion, however, is that it is a lot of money to spend when you can achieve the same results without the high price.) We are talking around $400 for a 12-qt model Kuhn-Rikon, vs. under $200 for a Fagor, or under $100 for the Presto aluminum. All pressure cookers on the market today must meet certain safety standards set by the USDA, so from the least expensive to the priciest, safety concerns become a non-issue in the final decision. Another important consideration is the availability and cost of replacement parts. The gasket will need to be replaced periodically, and sometimes other parts go missing or become broken. Be sure your homework includes this information. Your cooker will be totally worthless if replacement parts cannot be found.
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click here-----> Miss Vickie's Guide to Modern Pressure Cookery