IMO the only way a spark plug is going to make more power (assuming a comparison of new plugs to new plugs) is if they take up more volume in the combustion chamber thereby raising the compression ratio. That said, I currently run NGK IX's in mine because they should retain full performance over a longer service interval. I previously experimented with side-gapped/wide-gapped conventional plugs vs. full-electrode conventional plugs & found no power difference.
