Well, overclocking is never the same, even if identical parts are used. One computer may be more susceptible to ripple than another, however, this can be corrected by using a quality power supply with active PFC and using a voltage stabilizer or a UPS. This will provide the most stable power flow.
A voltage stabilizer or UPS will not have any effect on PSU ripple. If the PSU is within specifications, the AC ripple will have no effect on overclocking.
Remember, the motherboard is going to take the 12 volts and run it through a programmable switch mode regulator on the motherboard to get the volt or so that the CPU needs. At that point, you will need lab grade test equipment to measure any ripple present.