If you're handy with tools, and familiar with wood working, and not in a hurry, then a kit will give you more satisfaction in the end, and give you a rudimentary education in to what some of the tasks in gun building are all about. I'm not familiar with the Crockett kit, but most (like the CVA) are 30-40 hour projects with the right tools. Some minor fitting and inletting is usually required, as well as sanding and finishing. One thing that almost ALL factory guns have on them however, is too much wood to be either svelte, or historically accurate (such as they can be). The kits will similarly have too much wood on them. If you're after something in the end that is closer to HC/PC, then no question, go with the kit. Just be aware of what you're committing to on the front end, and above all, be honest and ask yourself if you're ready to make the commitment. If you start with a finished gun and then modify it, you're really starting with a kit and stripping and re-doing a lot of what was already done for you. By the time you buy the chemicals, sand paper, finishes, etc, you'll probably have about the same amount of money in the kit as the factory gun though.
If you're mostly after having a gun to shoot, in something of a hurry, and aren't that interested in the building process, then go with a finished piece, even though it won't be as good of an end product as you could make from the kit, and you won't get the education the build provides.
So the final answer really depends more on you and what you're looking for than it does the general premise of the original question.
It's kind of like an investor asking what kind of an investment they should make. The answer is, it depends on...