O ring chains have an O ring to seal lubricant in and keep dirt and moisture out of the rollers on the chain.
This greatly improves the life of the chain (if it is maintained correctly). However, as with most things there is a down side. The O ring creates more friction within the chain and therefore saps more power from the bike. In order to reduce the friction some companies replace the O ring with rings that have an X or even Z shaped cross sections, which have less surface area touching the moving parts of the chain. Many race teams use non O ring chains in order to maximise the available power and then change them after every race.
So to answer your question which is better – it depends on what is important to you.
– power loss?
– long life?
– cost?