PDF is just as good in the sense of being able to represent the documents people want to (arguably better, if only for transparency, compression (including JPEG), and (usually!) the ability to search for and select text). PDF does have many other additional features that people disagree on the value of, many of which are not supported by most PDF viewers. Being a full programming language, PostScript is technically much more powerful in many ways, but it turns out that's no longer very useful for most purposes (computers are much more powerful*, storage is cheap, networks are fast, most documents are viewed on screen, etc.).
* I've heard of people writing programs in PostScript to take advantage of printers' fast vector processors instead of running them on (at the time) comparatively slower PC CPUs, a bit like the early days of GPGPU.
PDF/X is just a PDF with interactivity/JavaScript/forms removed and the layout instructions rationalized and colorspace for RIP fir commercial printers
* I've heard of people writing programs in PostScript to take advantage of printers' fast vector processors instead of running them on (at the time) comparatively slower PC CPUs, a bit like the early days of GPGPU.