I hope that having this on the web may benefit other new users of Otter in some way. To find how to get and use Otter and the theorems mentioned, check out the Otter web site at Argonne . After building a table with many of Otter's results it appears that comparing speed and number of clauses generated is roughly equivalent. The number of clauses generated is assumed to give us an idea of the actual search space, since we would have to enumerate al possible results to get the real search space which is often not feasible. This is because binary resolution is complete with factoring, and Otter automatically enables factoring when the user selects binary as the type of resolution.
Binary solution is slow, compared to other methods of resolution.
Hyper and especially unit resolution are fast. They can generate new interesting clauses very quickly by combining steps or assembling several clauses in one step. Hyper and unit resolution don't always succeed in finding a proof. Sometimes however, combining the two enables Otter to reach a proof where each failed on its own, with a very good run time. Combining hyper and unit resolution with binary resolution gives better run times than when using binary resolution alone.