1st generation PowerCores are: PowerCore Element / PowerCore PCI. 2nd generation PowerCores are all the others.
Generally speaking, it depends on the nature of the plug-in. On average it is around 50% more. When using plug-ins that take up 1 whole DSP no matter what -- for instance Virus or Intonator HS -- you will be able to run the same amount per DSPs. But if you were to run plug-ins using the RAM on the 2nd generation PowerCores, like the reverbs or delays, you can run around 4 times as many, when comparing to the 1st generation PowerCores. Please note: some of the plug-ins that we are planning to do in the future might not run on the 1st generation PowerCores, but they will run on all 2nd generation PowerCores. Please see this answer for an overview over the DSP usage for each plug-in