I would generally agree. But, in my case, I had to get deep into this exact question for car parts, and convince the customer that it was as good as galvannealed steel. The customer test specs were severe, not only salt spray, but cyclic salt spray involving wetting and drying. And the phosphated/parkerized with baked enamel paint performed immensely better than plain painted (same everything including paint, just no phosphating), including paint adhesion under rock chipping ("gravelometer"). On bikes, the difference may not be nearly as much if the bikes are not subjected to as severe use as those car parts; Our customer, located in the rust belt with salted roads, made a big push to make their cars not rustbuckets like they had been. I don't think most bikes are in the salt much, unless winter commuting where roads are salted, or living by the sea (I rode for several days along the ocean on sunny days, geez, I couldn't believe how much dry salt the bike and my clothes picked up, just from the onshore winds over the beach).