i think it's relative to where you run. in a smaller, more technical track, electrics will likely be faster coz of acceleration out of corners. for huge tracks with super long straights, nitro cars would probably have an advantage. an ep car may have the speed record but then again, that wasnt your run-of-the-mill ep car. i mean most of us here probably never even ran (and probably never will) more than 7-cells in our rides let alone 20+!!!
quite honestly though, both ep and gp cars nowadays put out so much power that even if you go with either class, theres plenty enough speed to satisfy any speed junkie's urge.
slap on the most wicked outlaw engine in an 8th scale gas car or strap on 6 cells on a 12th scale ep car with a 6 turn motor and im sure most of us here will have their hands full trying to handle or max out the speed.