I haven't tried the black oxide process in my shop; I would imagine it has about the same durability and results as using some of the (better) cold blue processes. The issue I have found, especially with the other-than-hot salts bluing vis a vis black oxide, is that the results are not consistent.
Parkerizing...if you do your part, the results are quite nice and it isn't all that difficult for most people to do. Now, parkerizing as you probably know in and of itself does not protect metal...it's just a way of prepping the metal to "hold" onto whatever anti-corrosion oils or greases gets placed on the metal. It kinda etches the metal, creates microscopic "craters" (for lack of a better term) to hold onto the oils/cosmoline/grease. If you prep the metal correctly, you'll get superior results. It's not as fussy as bluing, and it's more durable than any cold process of bluing or blackening, in my experience.
In all reality, there is no way as of yet to "get around" in any CONSISTENT manner either of the hot processes, be it parkerizing or bluing. It is what it is. The only thing that I've seen come along in the last 20 or so years that yields consistent results other than the aforementioned two is the moly-type coatings, but they are still a hot process to cure, and there is still metal prep that needs to be adhered to for good results.
That's my .02.