The biggest performance advantage is not a new A9 vs A8 but memory speed and size. With modern software it is a critical to keep all stuff in memory vs moving it back and forward to slow (!) flash devices. At least this is a biggest drawback of N900 - it's 256MB can't keep all applications and Nokia forces an intensive swap with slow (19MByte/sec) eMMC.

With application sizes around 100MB it takes epoch to reload a running application after some daemon forced it's swap out to eMMC.