In general if there's a reasonable doubt about which is primary or even significant discussion about if a primary topic exists at all its usually best to have the DAB page at the base name. However in some cases like Kansas City and Salford where there are several articles about 1 concept its best to have a article describing it per WP:DABCONCEPT since readers are more likely to be confused by the DAB since they won't necessarily know what link to click on and landing them on an article describing the topic with links usually makes more sense.
Part title matches edit
If there is only 1 or 2 other topics of a similar importance such as Mundham v North Mundham/South Mundham then it might be OK to have the only full match at the base name with links to others or even a link to a DAB if there are more. If the PTMs are much more important than the full match it might be better to have a DAB at the base name.
SMALLDETAILS edit
SMALLDETAILS causes a lot of confusion and controversy, those who don't know it exists often think that both titles should point to the same place while those who do know it exists think it automatically allows any similar title to point elsewhere. In reality it they should usually be assessed as with any other title per WP:PRIMARYTOPIC and its common for 1 of the 2 articles to be ambiguous with both terms while the other 1 is only ambiguous for 1 of the terms. In general if one of the terms has a more obscure/harder to type part in the title and readers type it they can usually be assumed to be looking for that title but the easier to type title will usually remain ambiguous since readers often won't know the topic has the variation or that Wikipedia distinguishes those details.
Capital letters edit
Capital letters are probably the most debated part of SMALLDETAILS, The most common situation is when there is an article on a general meaning at a sensitive case title like Friendly fire or Duck sauce and then a DAB or even another article at the title case version like Friendly Fire or Duck Sauce. Generally if a reader is bothering to type the 2nd word in upper case there probably looking for a proper noun so its usually best to land them on a DAB page. However since many readers won't know Wikipedia search is case sensitive or otherwise won't bother to capitalze landing them on another article sometimes doesn't work, see Talk:Grateful dead (folklore)#Requested move 5 March 2018. However like Apple sometimes land the reader on the general meaning per PT#2, see Talk:Man bites dog#Requested move 28 November 2019 for example. Note that its not possible to distinguish between cases with the 1st letter in titles/search for example apple/Apple and cars/Cars aren't distinguishable and even if they were its more likely this would cause confusion and work less well because generic meanings are usually capitalized at the start of a sentence.
Diacritics edit
Most English speakers won't know how diacritics work and even those that do know its often difficult to type them since there not on English keyboards, see Talk:George Puscas (sports writer)#Requested move 1 December 2019, Talk:Cesaro (wrestler)#Requested move 23 April 2019 and Talk:Nelson Oliveira (cyclist)#Requested move 4 May 2020 for example. However anyone who does search with diacritics can usually be assumed only to be looking for that topic.
Plurals edit
Most of the time the singular and plural forms of a count noun point to the same place (such as Car and Cars) however since people are more likely to search in the singular it is sometimes better to put a DAB there (or redirect it to one). However there should generally not be a different topic at the plural form. However sometimes in cases where there is a DAB at the singular base name such as Orange the plural is (relatively) unambiguous because there is only 1 count noun at the singular title which means the plural can redirect to it such as Oranges going to the fruit. Generally the plural form of a countable noun should never be treated as a part title match when assessing primary topic however as noted we can usually assume that the vast majority of people will use the singular form when searching and thus we don't need to treat the noun as if it had that title. If a noun is placed at the plural form such as Stairs the singular for (Stair) should also not be treated as a part title match.
Stylization edit
Similar to diacritics if someone is including them they can usually be assumed to be looking for that topic with the stylization but not the other way round.
US cities edit
US cities are usually titled with the state (such as Gloucester, Massachusetts and Hodgenville, Kentucky) even if they're unambiguous unless they're in the AP Stylebook. Articles in the "city, state" format should have the plain name redirected to the full name. In most cases, such as for Paris, Texas, that will be impossible, because the base name may have other uses, in which case a DAB entry or hatnote should be used, Paris has a hatnote to Paris (disambiguation), Bowmore has a hatnote to Bowmore, North Carolina, Stockton, California is included on the Stockton disambiguation page and Bothell redirects to Bothell, Washington. When weighing a U.S. city against other possible primary topics, the U.S. city should never be considered a partial title match if the base name of the city is the same as the term being considered. However for the same reason as plurals discussed above, readers and editors are used to seeing US settlements with the state included, they can be expected to search/link to them with the state more often and thus usually don't need to be treated as if they had that title and unlike in most other countries Americans often consider the state to be part of the names.
Primary topic swaps edit
Since incoming links from external sites etc will be left pointing to the wrong page if a PT swap takes place its usually better to put a DAB page at the base name instead (at least for a while) note that this is less a a problem when there is only 2 topics or the other topic is already linked on the DAB.