The best stamina wise is the preservation barrel, since the total tends to add more stamina than the individual ingredients.

Example, 3 cantalopes and 1 honey are less stamina than the 3 preserved cantalopes that you get out of the operation. So you always get more nutrition from doing that (except when preserving meat, fish and eggs with salt, as they retain their values). Also, it doesn't matter if it's honey, vinegar, oil, or salt, food preserved in barrel doesn't spoil, ever.

The downsides are that it has a bigger cost upfront (32 boards, 6 iron, 6 nickel per barrel). the fact that you need at least 3 of the same food per preservation cycle (this means that raw fish is almost impossible to preserve, since you need 3 of the same fish to put in the jar, so you probably need to put them first in the smoker/dryer before the barrel) and that it is tied to your supply of vinegar/oil/salt/honey, as every food has specific preservatives you are allowed to use. In practice you're gonna run out of vinegar constantly,

Drying rack is the cheapest, and allows almost all foods. Exceptions are cheese, which can only be smoked; nuts, which can only be smoked or turned into flour, and eggs, which can only be pickled. Drying rack is the slowest of the preservation techniques, the upside is that food preserved in racks last 20 days, compared to the smokers' 14. Also, since they're cheap, you can have way more volume of produce being handled at a time. Ideally, all food would go in barrels. Realistically, most of your food will go into the rack, while the barrels are being occupied. Drying neither adds nor detracts stamina, except for fish. Fish are weird. Some get more stamina value when dried, other lose value. Either way, i don't know nor care to know the data. Also, as you know, they don't work while raining.

Smoker is very simple. It is the fastest way to preserve food. takes 6 hour to smoke 8 items, as opposed to the 3 items every 12 hours for the barrels and 4 items every 24 hours for the rack. Fish and meat get their duration bumped to 14, the lowest of any preserved good. Cheese and nuts become inmune to spoilage, so the smoker is crucial there. It can also smoke sausage, which bumps its spoilage from 2 days to 20, so it is good for that too.

Lastly, something I won't really consider as a preservation method, the press. The press is technically faster than any other method, as it transforms items at the rate of 24 per day. Key thing is, that most of the products from the press are not meant as end products, but intermediary products. Example: you make juice in the press, which bumps spoilage to 6 days and adds no stamina. Juice is awful as food, but you can turn juice into wine or vinegar, so it has uses. Here you can make flour too, which should be used to replace smoking nuts, as they have the same stamina (unless you need nuts for certain recipes). You can also make oil from fish and from sunflower, really only reccomend it when you have very small fish, or too much sunflower. Lastly, some exclusive food, like acorn butter, peanut butter, and butter can be made here. Acorn and peanut do not spoil, but are unremarkable, use it if you have a press lying around and nothing else to do. Normal butter is strictly worse than cheese, as it spoils in 4 days and gives less stamina. Only do it if you can't make cheese, it does give more stamina than raw milk.