Personally I'd go for a Jap brand exhaust because of the massive experience they have in dealing with Skylines.
You probably won't notice any difference in power but I'd suspect things like quality of the bends and fitment are better in the Jap-made one.
As for sound, there is no real way to know. Maybe go on a cruise or dyno day and listen to exhausts and see if there's a sound you're attracted to then ask the owner about the system.
I have a 3" Kakimoto catback, standard cat and JustJap front/dump pipe combo. The sound is not too loud and if you search around SAU, you'll find that many of us recommend Kakimoto for a decent level of sound.
However, if I had the money I'd go for an Apexi N1 Catback. My brother had one on his FTO and it sounded extremely good.