All long term preppers are gardeners in the process of becoming farmers. The only real security is learning how to grow things or raise animals or fish from aquaculture. You can only eat from a can for so long, and then your supplies run out. One way is not superior to the other. It is both/and not either/or. Because we must preserve food for the period post-harvest until the next harvest (usually early November until early June[8 months!] through early November), then learning canning, dehydrating, and pickling is a necessary step for a diverse healthy diet.
Most seeds today are hybrid. In order for the seed company to make money, they need to create seeds that they alone can sell, otherwise a wise gardener would simply save their seeds from year to year. If one saves hybrid seed, there's a good chance that it will still germinate, but may not germinate as well or the plant may revert to earlier varieties or it may be sterile or it may produce less yields.
A long time ago, our ancestors traveled to the New World. They liked certain foods like chicory or dandelion or a particular variety of squash or wheat or whatever. Since they often came from far away places like Ireland or Italy or Norway or China, they had certain cultural foods which they enjoyed, and so since those foods might be hard to come by in America, then they brought seeds with them from far away. Others began in New England and the Atlantic coast, and then because of Westward expansion, brought tree seedlings, seeds, and transplants and kept them alive until they could be replanted in their new soil. The West began in fits and starts in Kentucky and Indiana (first cowboys and train robberies), and from their spread North and South and ultimately West to the Pacific Ocean.
In some cases, varieties of seeds now called Heirlooms were originally brought from local areas in foreign countries and then over generations were brought into entirely new frontier areas of the USA. To be considered an heirloom, the species has not changed through open pollination, is at least 50 years old but may be as much as 100+ years old, and has been deliberately saved. These are the varieties that were carried by immigrants.
Of course, some people stayed in their respective nations, and they too saved Heirloom seed. They continued the traditions of their ancestors or they decided to plant those good tasting varieties. In many cases these plants taste better, but perhaps since most people purchase their food in grocery stores, plants are more uniformly chosen by the companies that ship them. Grocers cannot carry 10 varieties of carrots, because as one increase the number of species carried, then more inventory will be not be purchased. Other varieties may taste great, but may bruise easier and so since shipping is a concern as well as ripening, then those varieties which meet a happy medium of storing well, shipping well, and taste reasonably good are most often chosen by the corporate farms to grow.
This means as a prepper and gardener, one chooses the best seed to purchased based upon your particular needs. You don't grow what works best for someone else, but based upon logic and personal decisions of taste preference. You do it based upon yields and drought-resistance. You do it based upon speed of growth and plant disease-resistance. You do it based upon whether you want a short bush variety or a long vine variety so it will fit in your garden space. You do it because a certain kind of carrot may “fork” (misshapen formation) in the dense clay of your area, while others may be more suited to it.
Having Heirloom seeds need not be more expensive. It may be that you can trade for them. Many gardeners or organizations may give them away or may charge a nominal fee for shipping and packaging. They want the variety to perpetuate since it tastes good or has some botanical quality or simply for historical reasons too. Other places commercially are setup for large varieties or may prepackage Heirloom seeds for preppers in order to best meet general needs. Do your research and make an informed decision based upon logic and emotional desire.
Please prayerfully consider purchasing good Heirloom varieties since they're non-hybrid. You then need to understand how those plants go to seed, deliberately help them to seed, and then collect the seed, and properly store it so it germinates in the next growing season.
Many gardeners purchase transplants now. They purchase them from a greenhouse since they don't have the time to start seedling, nor have the ability, nor the patience to germinate and tend them. When beginning to germinate the seeds, they make mistakes. Their plants are “leggy” because the seeds are not warm and have adequate sun, and then they grow improperly. Don't assume you understand what the seeds need to germinate, but carefully research this process.
Otherwise you'll lose valuable time. You can't simply plant seeds in a cold garden with inadequate days of sunshine or improper moisture. Many areas have unusual growing seasons based upon typical periods of light, rain, heat, etc. Say you live on a mountain. Maybe you live in an arid environment. Perhaps the soil is poor and doesn't contain the proper nutrients. It might be that the chief cause is YOU and your lack of ability, concentration, and lack of research.
It may be that you deliberately do things like mini-greenhouses in order to germinate them well, or you might end up extending your harvest like building cold frames. Think a little outside the box to have the best growing season for your family. Agriculture is an art as well as a science.
All primitive people could grow crops from seed, it's simply a matter of desire and motivation. In a collapse, you'll be producing food from a garden, or foraging for it. Since a plant may grow only seasonally or only if a particular niche, then foraging is very much like hunting. Don't count on finding enough food from the Land. This isn't how Nature provides, because like it or not, most of us are so disconnected from the Land that we can't or don't see where it grows anymore.
One of the great joys as a gardener is a “volunteer” plant. Seeds will naturally fall upon fertile soil, and may spring up on it's own. I've had many of these, and some were strong and ended up growing just fine until harvest. Others will not be so great and will produce less. Some may grow where it's not ideal or wanted. They may come up later than your artificially germinated plants. Not all plants can be transplanted. Realize that plants will shallow root systems may end up getting “shocked” by the change in climate. Read and see if it possible.