Why a pressure cooker?
Easy - time. Cooks things much faster. Boiling point of water in a pressure cooker (at 15psi) is a mere 250 degrees. Which means you can boil things in 2/3rds the time. And some other impressive things - a 6-hour stock in an hour.
Rules for pressure cookers
- Don't low-ball the price. You're talking about something that will hold boiling liquids/food at pressure. As in bike-tire pressures. The last thing you want is for it to give - it can hurt you, maim you, and at the very least make a mess of the kitchen that will be Epic.
- Same goes for used. Be safe on something like this.
- If it feels cheap, it probably is. You want heft.
- You want Stainless Steel, not aluminum. Aluminum will pit and hold gunk within - not a happy thing.
- 3-layer bottoms. Makes it cook more evenly.
- Bigger is better, you need room for the steam to build pressure. Supposed 6 quarts is the magic number.
- Get a modified-first-gen (pressure valve) or second-gen (spring valve), not a "jiggle top".
- Expect to spend between $70 and $250.
Brands I've seen recommended: Fagor (budget pick), Kuhn Rikon ("mercedes of pressure cookers"), Magefesa, and WMF (brand used by Alton Brown, but man that's pricey).
Either the Fagor or the Kuhn Rikon. Fagor's about $50 less, but I think either will be a good choice. The way I figure it, I cheaped out once on a different piece of cookware (a cast-iron skillet), and I might as well throw it out... tried seasoning it for years, and it still has yet to taste as good as the Lodge Logic we bought.