You can't really compare a 1Ghz snapdragon to a 600Mhz Arm A8 using clock speed alone, they are completely different processors and those numbers don't really mean much of anything unless you compare them to processors of the same family.
If you look at Android on the Nexus One and Maemo on the n900 you would be hard pressed to find a performance difference, because the major difference is the operating system.
Also we already know from the M6 slideshow that the next device will be built on the same hardware platform, OMAP3, OpenGL ES, etc. It also specifies that multitouch will be available for capacitive touchscreen devices. indicating that it will also still support resistive touchscreen devices (Why wouldn't it?). This means the is no reason to assume that Nokia would need to maintain two maemo for two architectures.