the locative construction in which the comparee takes the partitive case (word order not fixed, but unmarked is [comparee in the partitive case] + [comparative])
When the comparee and the comparative are single words, both constructions are common, and the locative construction is probably slightly more so, especially when the comparee is a common word (such as a personal pronoun).
As the comparee or the comparative gets longer, there is an increasing tendency to use the particle construction, which is the only option with relative clauses (like in the usage example above, directly under the definition).
“kuin”, inKielitoimiston sanakirja [Dictionary of Contemporary Finnish][1] (in Finnish) (online dictionary, continuously updated), Kotimaisten kielten keskuksen verkkojulkaisuja 35, Helsinki:Kotimaisten kielten tutkimuskeskus (Institute for the Languages of Finland),2004–, retrieved1 July 2023
1936, N. A. Iljin and V. I. Junus,Bukvari iƶoroin șkouluja vart, Leningrad: Riikin Ucebno-pedagogiceskoi Izdateljstva, page25:
Kuin ono sooja vesi.
How warm the water is.
1936, L. G. Terehova, V. G. Erdeli, translated by Mihailov and P. I. Maksimov,Geografia: oppikirja iƶoroin alkușkoulun kolmatta klaassaa vart (ensimäine osa) [Geography: textbook for Ingrian elementary school third grade (first part)], Leningrad: Riikin Ucebno-Pedagogiceskoi Izdateljstva, page 3:
Töö saatta tiitäkuin suur ono maa, millaist hää ono formaa ja mitä ono hänen pääl.
You will be able to knowhow the earth is big, what kind of shape it is and what is on top of it.