68040 does 1.1 MIPS per clock, 68060 does 1.33.
A person also has to take into account that the '060 runs at a higher clock rate, plus its superscalar architecture. a 50mhz '060 is probably on average 1.5 times the speed of a 40mhz '040, but on occasion it's closr to 2x the speed. While higher clocked '060's are faster they dont scale well in some situations due to ram bandwidth being a bottleneck.
The difference is definately noticable, although dvd playback is still too much for an '060, especially when using aga.