A candidate to be the best analysis program is the latest version (version 1.6) of Critter created by Richard Vida. It is free and very powerful; some think it may be best for endgame analysis. It’s certainly no scientific test and proves nothing, but I ran a 2-game 5-minutes match against Houdini 1.5 and Critter won both games so it seems it’s certainly worth further investigating its possibilities! DownloadOne test I think might be helpful in considering the strength of engines is how they perform in Fischer Random Chess because they are in no way influenced by book openings and Critter 1.6 does quite well. The results at Computerchess for the top 5 engines in FRC are: 1-Critter 2-Houdini 2.0 3-Stockfish 4-Rybka 4 5-Naum
BTW, does anybody know what happened to Naum?! The website simply shows a tombstone with the inscription “Game Over.”
Check out the results of testing at Computerchess.