As others have pointed out, digital voting systems can be hacked, exploited, or otherwise derailed from centralized location. They also can contain subtle software errors.
Paper ballots can have problems like we saw in Florida (hanging chads).
When I was growing up, we had big mechanical voting machines. I have no idea how common (or uncommon) these were in different parts of the country. The machine opens up and has a set of retractable curtains. You walk through the open curtains and then pull a big lever that closes the curtains behind you. Then you vote by flipping mechanical switches for the candidate (or yes/no for policy ballot). When you're done voting, you reverse the big lever. This action increments the machine counters based on your votes and opens the curtains for you to exit. Once the polls close, the polling folks simply sum up the counters across all the machines in the polling station.
The downside is that the machines are big and heavy to store and move. I'm sure they're not cheap for the initial purchase. However, they're efficient for tallying yet very difficult to hack. In my opinion, they're the best overall voting mechanism.
Paper ballots can have problems like we saw in Florida (hanging chads).
When I was growing up, we had big mechanical voting machines. I have no idea how common (or uncommon) these were in different parts of the country. The machine opens up and has a set of retractable curtains. You walk through the open curtains and then pull a big lever that closes the curtains behind you. Then you vote by flipping mechanical switches for the candidate (or yes/no for policy ballot). When you're done voting, you reverse the big lever. This action increments the machine counters based on your votes and opens the curtains for you to exit. Once the polls close, the polling folks simply sum up the counters across all the machines in the polling station.
The downside is that the machines are big and heavy to store and move. I'm sure they're not cheap for the initial purchase. However, they're efficient for tallying yet very difficult to hack. In my opinion, they're the best overall voting mechanism.