For the rs7 plugs, between the two, it's worth noting that the beru are side firing and the NGK are top. I just swapped my 7,000 mile berus for NGK and the difference is negligible. Smoother, on the new plugs, but had both been brand new, i'd say you wouldn't be able to feel the difference.
NGK can be gapped where beru are not supposed to be. Both came out of the box, pre-gapped and equal to one-another. I think I got 0.025" on the NGKs I just dropped in. IIRC, beru were pretty close to that too.
FWIW, I spray about a gallon of 50/50 water and meth per tank of fuel. And my berus were starting to show a little (tiny bit) of idle roughness.
meth is a hell of a drug... on plugs
Replace your plugs more frequently on highly tuned and/or methanol consuming cars. Most folks say 10k. I went on feel and the new plugs absolutely smoothed both idle and acceleration out for me.