A stone lets you control the angle and remove exactly as much steel as you need. A pull-through sharpener has fixed carbide or ceramic wheels that set the angle for you and scrape metal away fast. Pull-throughs are quicker and easier; stones give a better edge and remove far less steel.
A stone abrades the bevel at whatever angle you hold. That is both the difficulty and the point: with practice you can match the factory angle, add a micro-bevel, or reprofile entirely.
A pull-through drags the edge between two fixed abrasives. It is fast, it needs no skill, and it takes the angle decision away from you.
Carbide pull-throughs remove a lot of steel per pass, which is why they work so quickly and why a knife sharpened that way for years gets visibly shorter. They also cannot follow a recurve and will damage one.
Ceramic pull-throughs are gentler and better suited to light maintenance than to restoring a dull edge.
If you own one knife you barely use, a pull-through is fine. If you own knives you care about, a medium and fine stone plus a strop will serve you far better and cost about the same.