Its neater, easier to use, plus it gives the user the advantage of knowing more information about the targeted process, such as the thread count, and not to mention see the modules loaded.
So let's say you coded a module unloader you could look at those modules inside that process and decided which ones to remove. This is particularly relevant now, because a previous Hackshield bypass was developed by removing modules. Correct me if I am wrong please.
Plus, PerX gives out false positives. My injector doesn't. My injector also sets debug privileges, which Perx probably already does. Hope this helps your decision.