I have never seen a large displacement V-twin sport bike run right with a single pipe.
If it was designed from the factory with two. It's best to stay with two.
They never sound right either.
Can't speak for other V twin sports bikes but the RC is effectively a 2 into 1 already, it just splits again after the collector back into two. My bike sounds very similar to the way it sounded with the twin exhausts, in fact I can't really tell the difference apart from it being louder. The gasses are mixed on the twin system, just as they are on the 2 into 1, the only difference is they split again on the twin.
Mine only made a slight difference on the dyno between the two systems, which was probably down to the better flowing headers on the 2 into 1. For me the weight saving is the reason for the 2 into 1, I have effectively removed over a third of the weight of the exhaust system, with a very small gain in power, but a better power to weight ratio.
If the factory parts are so good, why do we all spend so much changing them for better ones? Why do race teams spend small fortunes developing better parts? Because OEM parts are a compromise between cost, ease of manufacture and meeting emissions/noise/safety, and various other criteria to make a profit, and meet regulations.