If you account for the difficulty of picking candidates only, then yes. Practically the difficulty of navigating and filling the ballot should be considered too. People would quickly become angry when confronted with a task to check half of the 870 checkboxes printed on a ballot when choosing among 30 candidates/parties in an election. Even if it weren't mandatory to decide on all pairs, merely finding all of the 29 pairs your favourite takes part in would be a frustrating task for most citizens.