Core speed or memory speed?

[CurlyWhirly]

Generally speaking when overclocking graphics cards, which is more important in being able to have a successful overclock - an increase in core speed or memory speed?

I think that the core speed is multiplied by the number of pixel pipelines to give you the total bandwidth generated?
If so I can see that having a higher core speed is an advantage here but what about memory speed?

Is a higher memory speed really that important?

 

[CurlyWhirly]

then see what the mem can do but you need a biggere increase in mhz for the same jump in performance.

So let's say that for example that I was able to overclock my core and memory by 50 Mhz in each case, then I would see more of a performance gain by overclocking the core compared to the memory?

If true then that answers my query. Thanks