Well for me its a combo of both. I've always played it in Drop D, but the custom is in E standard. For the most part, the only difference is in E Standard you would use 2-3 fingers to hold a power chord, while Drop D you would only use one, and all three notes would be on the same fret. But on top of that, Drop D is a full step lower on the 6th string, so there is a different sound if nothing is fretted. So just by watching how she is holding power chords that involve the 6th string is a good giveaway on if it is E Standard or Drop D. As for sound, like I said in the chorus there is a part that is a D chord, which is the open three low strings, and you can't do that in E standard.