The best benefit I've heard about paper voting is the mechanism by which trust in the count is ensured.
With paper voting, all votes are counted by several people, with oversight and random recounts. It is _possible_ to cheat, but it would require a local conspiracy for a limited number of votes.
With electronic voting, the counting is done by machines and the mechanism is obfuscated and unverifiable. If it's working correctly, it should be perfect; but if the machines were hacked, it could be done through a network and the impacts could be massive. It would require a large conspiracy to pull off, but the number of votes that could be affected could change an election.
So in summary: paper voting = higher chance of small irregularities, with limited impact; electronic voting = lower chance of massive irregularities with election changing consequences. In paper voting, the trust is distributed, while in electronic voting, it is centralized.