I have owned both a quick Silvia, an S15 with 280 hp ATW, and now an R32 GTR at the limit of the std terbs with 340 hp ATW (both on the same dyno). Whilst the GTR runs the faster time slip, the S15 funnily enough felt faster due to the steep power curve. The S15 also had the higher top speed (256 km/h) compared with the R32 (245 km/h is the best so far).
All in all, however, the GTR is a much more enjoyable car to drive hard and feels far more predictable when exiting a corner on full noise (no surprise here with the ATESSA).
I have also been chopped a few times by Silvias (and even Summoner's V8) when caught at the lights off boost. But as gtrken says, when challenged in a rolling start it's a different matter. Gotta love the feeling when challenged on the freeway and there is plenty of room - drop back to third straight into full boost at 4 grand on 100 km/h, hold this gear until the taco hits 8 grand and more likely than not your adversary will be a distant object in the rear view mirror.
Both the SR20 and the RB26 are great engines that will go down in history as a tribute to Nissan.