At DC steady state voltage and current are directly proportional, but under transient and high frequency conditions they are not. The equation for an inductor is:
V(t)=L*di/dt, where di/dt is the rate of change of current and L is the inductance.
Basically this states that the rate of change of current is proportional to the Voltage applied and the inductance. If current changes instantly it would require an infinite voltage. The dv/dt however can change instantly. For a capacitor the terms V and I are transposed.
An applied voltage pulse would look like this in the time domain
__|"""""|____
and the corresponding current would look like this
___/"""""\___
The voltage just represents the force, but the current represents the actual heating and energy. I.E. the spark exists as long as there is current flow.
The added inductance might increase the spark duration, by slowing the rise and fall times on the current through the line. This could be countered with a power factor correction by adding a parallel capacitance, to bring the current curve closer to what the OEM wires would look like.
I get what you're saying though, this level of detail is overkill, and in reality pointless unless you analyze the entire system, from the battery out, but I think there are advantages to the NGK wires and I'll probably try em out. For one my OEM wires have infinite dc resistance, indicating there is a small air gap somewhere within the wire. I'm mostly looking to get smoother operation at idle rather than supposed horsepower gains.
An interesting read:
http://www.vtec.net/articles/view-article?article_id=8680