An interesting thread, it makes sense to me that the bait of choice should be matched depending on that given circumstance for the best success. Mackerel head is a good bait if the area is plagued by dogfish or if it's a known area where discards are thrown back e.g. piers, by fishmongers, by bait tables. Similarly, when the spider crabs plague up the estuaries or on the open coast, spider peelers if you can get hold of them as well as normal peelers in season etc. Most of the time in estuaries I fish squid baits, mainly due to striking the balance between being more resistant to crabs, attractive to the bigger bass, availability, and cost. It comes into it's own in Autumn, often combined with a wrap of lug, suggesting we as anglers are best off matching the hatch.
Something I want to try more as I haven't given it much of a go yet but hear it's superior is live baiting for bass. Hoping to give it a go this year, mostly off the steep beaches like Chesil. My best bass was from a mackerel bait that had been stripped to the bone, but I'm sure that was more luck than anything and maybe, as mentioned above, was likely due to the crabs which could've caught the bass's attention. Hear quite a lot that bluey is better than mackerel where both are used in general situations, and also that gar is very effective.