pocket hole joint Vs. cam lock joint - What's sturdier?

In the absence of clarification from the OP I'll Answer this with a given set of assumptions.

The basic answer here is pocket-hole screws, and by a pretty large margin.

It's not simply that the screws themselves are so much more secure than a steel rod of some kind intersecting with a cam¹, it's that pocket-hole screws tend not to be used in isolation. The norm for screw installation in pocket holes (and actually much assembly of furniture using screws) is to both glue and screw. And the glued joint does a lot of the heavy lifting when it comes to joint strength, particularly so in solid wood which edge-glues far more strongly than plywood does.

In addition to outright strength, there's the issue of flex and other movement in a joint. A joint that can shift even slightly is always at risk of becoming looser over time if it's stressed, but even from normal day-to-day loads being applied (minor stuff, like leaning forward into the surface of a desk as you work at it), as well as from seasonal wood movement².

And this is precisely why screws are rarely used by themselves in quality furniture work; not necessarily high-end stuff, just anything intended to last. Because they allow for some movement they tend to wallow out their own holes and you enter into a cycle of damage — movement leads to wallowing which allows for even more movement, and so on.

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¹ At least in a fresh installation, where everything is done well.

² So just sitting there unused something can become a little less tight and solid than when it was last used.