To add to my above comment, the note-off is not easy to control, for example I would find it difficult to have a note return/note-off value of '50' (for example) multiple times, note-on however I can fairly easily match velocity on repeated notes (at least close to).
Note-off can be confusing at first, a loud note-on followed by a long/slow release (low value) note-off. This is something that requires practice to achieve the same result twice, or at least to be aware of this when playing, although this is the same on a 'real' piano.
As for keyboards with note-off function, I can only guess the technology is similar in other keyboards to the VPC1 (which I own). I would not buy a keyboard for note-off capability alone, but it is a feature I am used to and would not now want to be without.
One thing to try is to have several note-off curves, each for an approximate note-off, example, a low value curve of 45 for a slow or quiet piece you are working on, and then use a different curve for a fast piece. Not perfect but it will give you an idea how this note-off feature works if you decide you require a keyboard with this function.
Nick