Not an expert, but afaik there's been quite a few studies showing that natural immunity is superior to the vaccine-induced one - I'm also fairly sure that virologists have theorized to that end even before the data became available for the following reason: the vaccine is 100% focussed on detecting the spike protein, so changes to the spike can result in evasive variants. Natural immunity OTOH is developed against more sites of the virus and thus provide a more broad and robust response to variants, present and future.