My (professional) opinion is that the main benefit of side gapping is for the place that sells you the plugs, since they will wear out much quicker.
A correct, properly gapped spark plug will ignite your air/fuel mixture just fine.
If you want to pretend to be doing some cheap high performance mods, you'll do better to index your plugs.
Though the benefits to a stock or slightly modified engine are most likely psychological (just like side gapping)
And the fuel thing
Dog and Sweat covered it quite well
