toplessFC3Sman

iTrader: (1)

both actually, but yea.

NZConvertible

Actually, it's touché (note the accent), so it's not spelt like douche. Half the people on this forum suck at English, so they should leave other languages well alone...

Even on the lightest street FC, the weight saved with a single system is still insignificant. The three factors that really matter are noise, cost, and personal preference (i.e. looks). A single will in general be louder and cheaper.

As long as we're comparing the same types of mufflers, two mufflers in parallel will be quieter than one single muffler.

True, but that's not really relevant here, because the discussion is about the configuration of the rear mufflers. Whether you have single or dual rear mufflers, you can still put additional mufflers in series with those if you want. If for simplicity we just look at two muffler positions, centre and rear, a "single" system could run one muffler in each position (i.e. two in series as you suggest), but a "dual" system could have one in the centre and two in parallel at the rear, which will be a more effective. The Fujitsubo dual cat-back I had used a single bullet muffler before the Y and two more bullet mufflers after it, plus the two big cans at the back.