As far as I know the 104s only come in the standard and XP. Go for the standard. Here's ZZPs description if it helps:

Mixture of nickel and copper-glass seal that bonds the insulator, terminal post and center electrode together, assuring full voltage
Chromium-nickel alloy ground electrode resists gap erosion
Copper-core center electrode sheathed in high chromium-nickel alloy for superior heat dissipation and durability
Longer insulator nose provides a longer path to control fouling deposits
The autolite 103 plugs are the ZZP team's preferred plug. They need to be changed out more often then the NGKs but performance and KR reduction is excellent. The racing version of the 103's has a back cut electrode and they feature nickle plating.