Black filled circles and triangles. These choices provide an interim step between Traditional Notation and the default WYSIWYP preferences. Sharps are represented by upward pointing triangles while flats are represented by downward pointing ones. The vertical placement on the staff is the same as the corresponding natural. For example, a C sharp is an upward point triangle on the same vertical position as the C natural. This maps to a key on the keyboard that is both a C sharp and a D flat. So, the same key can be represented by a downward pointing triangle on the same vertical position as the D natural. Traditional Notation works in a similar way wherein a sharp is played by pressing the black key to the right of the natural and a flat by the key to the left.
If you are planning to switch to using Traditional Notation, then this might be a good way to not drift too far from its design and to get used to making these last moment mental conversions from natural to sharp and flat. Using symbols that are black filled makes the noteheads really stand out on the page and perhaps easier to read by some.
Another factor to consider is the use of color-coded chords. The filled notehead makes the colors stand out in order to be more easily recognizable.