Pressure cookers are like popcorn, you'l won't be happy with just one. I use a 21 quart pressure canner for both pressure canning and as a hot water bath container that resides in the garage. And yes, I have the seal checked annually by the Extension Service. Right now I use an countertop cuisinart pressure cooker nearly daily. I also have several pressure Kuhn Rikon cookers that were put back when I tried a combination induction, radiant smooth top. With a smooth top you heat the pressure cooker on one burner then once pressure is achieved you move to a burner heated on low. I don't like the extra attention and it's difficult to keep the heat low. Which is fine now that Viking discontinued and no longer provides parts for the stovetop. So I'm now thinking about my choices: propane, induction or radiant. If I didn't have stainless lined copper pots that I loved then the decision would be easy but propane would be easier with pressure canning.
