The Mac Mini does have altivec, though. Saying it's nearly 3x faster is not accurate, as most apps don't benefit from Altivec to that extent. Of course if all you want to do is use Altivec apps, then yes, it's fair... but that's not what the poster asked.
Yes, the Mac Mini is faster, though.... just not 3 times faster for most things.
Any application having graphics or sound output benefit from AltiVec. It is not sitting there unused waiting that some app has specialized AltiVec routines.
But yes, not 3 times faster for most things although Mac Mini G4 will be faster in general.
