Could you explain in more detail why this is better than vinegar. I am unfamiliar with the term. Also, can fish be "lactofermented"?
Lactofermented means fermented with lactic acid-forming bacteria. Traditional pickles (actual cucumber pickles, I mean) were made this way, for example, and you can still find fermented pickles here and there. Bubbies sells them, for example, though I don't remember offhand whether they're pasteurized, which would eliminate any probiotic benefit. Korea's traditional fermented condiment, kimchee, is made with napa cabbage and all sorts of other ingredients, including seafood, often enough. Salt shrimp is one traditional ingredient. And I've made pickled salmon and pickled herring by fermentation on many occasions.
The only commonly available lactofermented food is yoghurt, but there are plenty of other dairy ferments, including kefir, and there's pretty much no end to the options if you want to experiment. I've bought and made all sorts of fermented vegetables, and many traditional sausages like salami were originally lactofermented too — that's where they got their tart taste.
Vinegar, though not bad per se, is sort of an empty calorie source by comparison, and of course vinegar pickles have no probiotic effect, whereas lactofermented foods are probiotic by definition.
Hope this helps.