Choosing between Knitting and Crochet for Yarn Crafts is something like choosing between Python and R for your first programming language. You can do most things in either, though some will be easier in one than the other. Unless you’re primarily interested in one of the things that is significantly more straightforward in one compared to the other, you should consider other factors like what expertise you have easy access to (e.g. do you have a close relative nearby who crochets, is there a knitting circle in your community, etc.)
You can also learn both, and some of the basic concepts like maintaining consistent yarn tension carry over from one to the other.
Knitting
Knitting is done with two needles, and stitches stay on a needle (or the cable between needles, if you’re using circular knitting needles.) If the stitches slide off the needle (dropped stitches), they can be kind of challenging to get back in order, especially if you’re doing a pattern that involves different kinds of stitches.
Knitting wants to be flat. Because stitches are worked across a flat plane (the knitting needle), it’s possible to mechanize knitting, which brings us to Machine Knitting. There are ways to knit things into three-dimensional shapes; heels on a sock are one of the most iconic examples, but by and large, knitting is less tangled up with topography.
Knitting standard Stockinette Stitch (knit on one side, purl on the other) creates a smoother-texture fabric than you get with crochet. It’s also a little easier to create stretchy fabric (in multiple different variations) than with crochet. This makes knitting a good fit particularly for socks, since the texture presses into your feet, and you need elasticity around the top to hold the sock up.
Crochet
Crochet is done with a single hook, and only the currently active stitch(es) are on the hook. This can make it simpler to make very large things, since you don’t have to store all the stitches on knitting needle(s). Having fewer things in your hands arguably makes it a little easier to learn.
While the details vary by the crochet and knitting stitches used, crochet uses more yarn than knitting. With comparable stitches, you can knit a piece using 60-80% as much yarn as you’d use crocheting the same piece. Because it uses more yarn, crochet produces a thicker fabric that’s less drapey than what you get with knitting. For that reason, some people prefer knitting for clothing, and crochet for stuffed animals, bags, coasters, and other household materials.
Topography and spatial reasoning skills are important for crochet in a way they aren’t for knitting. If those aren’t your strong suit, you might find it frustrating to realize that what you intended to be a flat circle has turned into a small tube.