Whilst there's some fabulous real tracks for piano, few of them cater for very slow ballads. I've tried to create ballads using real tracks with a tempo of 50 or less and they just don't sound good. I have to use midi. Somebody mentioned in a wish re Hawaiian real tracks ( myself included ). Atypical Hawaiian ballad is very slow & smoochy as are many celtic airs.
In the 3/4 waltz tempo for example the piano just doesn't cope with tempos below 40 even using 1/2 time. For my latest composition I've had to use a real keyboard player as the piano & guitar both struggle with the slow tempo. To be able to use biab I've had to play it twice & speed it up 2nd time round and increase the tempo to 50