When I was beginning piano lessons as a young child, I was instructed to play with elbows slightly above the keyboard, arms parallel to the floor.
A decade later, as a teenaged pianist, I began studying under a different teacher, who sat with his elbows below the keyboard. He changed the way I played completely, from a technical perspective. I became increasingly exposed to the recordings and videos of Horowitz and Gould. Favouring their respective tonal palettes over those of most contemporary pianists, who I noticed generally sat much higher at the keyboard, I began experimenting with a lower seating position.
Throughout my undergraduate degree in piano performance, I sat low-the very lowest setting on a standard professional artist bench.
Since then, I began sitting even lower. I began cutting the legs shorter on my benches, eventually settling at the height of 14 inches- the same as Gould, I believe. I used this bench to record the op. 10 and 25 Etudes by Chopin-my first real recording project (rather than live performance on video) and I am quite satisfied with the results so far, tonally speaking. I've posted about 1/3 of them so far-they are in the audition room if you fancy a listen.
I must say though, although I favour this sittting position for Chopin, Baroque, and certain other periods, I feel more comfortable at 15.5-16 inches when working on my newest project, the Symphonies of Beethoven arranged for solo piano by F. Liszt.
Of today's pianists I prefer mostly the ones who are sitting a bit lower, with the exception of Sokolov and a few others. I find many pianists who sit high have a rather limited range of F and FF, and are more prone to having notes not 'speak' at the pp levels.