This if the topic of much heated debate. Some prefer the series mod due to the double battery voltage and the fact you don't have to build such low ohm loads to crank up the voltage. Others stand by the parallel, since the amp load capability is increased and claim it is safer because of this. I have had both and currently own both, but I want to see what the community thinks. If you claim one is better, then give reasons why not just "x" is better. I true I'm looking forward to what the community think on this subject.