See Can.
Open Can.
Watch worms squirm.
Sharpening knives is one of those things that you can put as much, or as little, effort into as you want.
The pull through sharpeners are OK and can put a serviceable edge on a knife. If you overuse or misuse them you can really damage a blade however.
The angle a knife gets sharpened at depends on a lot of things and is essentially a trade off between durability of the edge and sharpness. i.e. the sharper a knife is the shorter the time it will hold that edge.
Different steel qualities also affect the sharpness. Japanese knives tend to be made with hard relatively brittle steel. This means that they can take and hold a sharp edge for longer, but more work is required to sharpen them. German knives tend to be made from relatively soft and malleable steel. They hold their edges for shorter times but are quicker and easier to sharpen.
Long story short is that you should match any pull through sharpener to the same country of origin for the knife, i.e. sharpen Japanese knives on a Japanese sharpener and German knives on a German sharpener. Going any further than that is just marketing guff.
However, if you want to get your knives truly sharp you'll need to learn how to sharpen your knives on a whetstone or get a more advanced sharpening system like the edge-pro apex.