Listen closer to what Apple said: 64bit processors can be up to twice as fast.
That is true, if you’re doing worth with big data on your phone, you’re going to see a big improvement from the jump to 64bits. However, for the vast majority of phone apps today and in the near future you are not going to see any major improvements from the jump to 64 bit. The processor is just plain faster than the previous one though, so don’t worry about that, but the speed doesn’t come from the wider instruction set.
In fact if Apple could (maybe they can?) turn on 64 bit support on and older phone, you would probably notice it being slightly slower in most applications, this is because it puts more pressure on the memory bus which is already a bottleneck in many applications.
Doing the 64 bit transition now is just future proofing. There aren’t many immediate benefits.
