The issue that quantum computers have is not so much that individual qubits get errors, but rather that quibits become entangled with the rest of the universe, erasing our ability to take advantage of any quantom effect. To prevent this, you need to very carefully contain the quibits to prevent them from interacting with anything apart from highly controlled manipulations. The more quibits you have, the harder this becomes. If you can replace this with quidits that have more states, you can do the same computation, while needing fewer particles, making containment easier.
The issue that quantum computers have is not so much that individual qubits get errors, but rather that quibits become entangled with the rest of the universe, erasing our ability to take advantage of any quantom effect. To prevent this, you need to very carefully contain the quibits to prevent them from interacting with anything apart from highly controlled manipulations. The more quibits you have, the harder this becomes. If you can replace this with quidits that have more states, you can do the same computation, while needing fewer particles, making containment easier.