I have a 2010 1200X shorty, and my brother is still riding my old 09 nytro rtx se that is a 136" with Cobra track and 144 studs, with an Excell header. My 1200 has a mbrp header, dynoport can, PCV, and clutched.
We raced a few times on the rail road bed, and its extremely close out of the hole, then I pull away slowly. We never race til top speed, but I've seen 105 on the speedo on pretty decent hardpack snow. I would think the 1200 is faster top end than the shorty nytro. We're not straight line high speed racers around here, so thats about the closest comparison I can give for straight up power/speed.
Handling wise it isn't even a comparison. Doo wins hands down IN MY OPINION.