The 448 core can be OC'd better than the 384 cores. In fact the 448 core is almost a 570 which has 480 cores and there shader clocks are almost the same and as you go down in the cards.
You will see that the Shader goes higher. So in general the core clock is the speed at which the chip (GPU) works at. The shader clock on the nVidia cards are always twice the speed of the core clock.
With AMD the core and the shader are both set together at the same speed. The memory clock is the speed that has to do with the memory chips and part of the memery bandwidth on the card.
The shader has a lot to do with rendering. It is sort of the math of the GPU so when the GPU get smaller or less like the 448 core vs lets say my 550 ti's. My shader is a lot higher than that of the 448 core.
So my card has to work harder to maintane the ballance with the core and memory. This is hard to explain. So I have shown a quote from another web sit and I will link you the wikipedia on what a shader is. I hope this helps and good luck to you.
shader clock : the shader clock is the as it sounds,its the speed at which the gpu can render and is much like the core clock,and the shader clock speed is most of the time higher than the core clock on the nVidia cards.
Look at the non-reference 560 Ti designs, factory OC'd to 900 Mhz. Among them you will find several models that have upgrade dPCB's and beefed up VRMs. The ones w/ 7 phases or more and the special coolers have been known to top 30% overclocks over the reference card speed.The MSI Hawk you linked is one of these
Yeah. The $220 GTX480 doesn't look good next to the $245 7850. The 7850 OC's well and you'll get that $25 back over time with the lower power usage. $200 for the GTX480 and maybe, but not with the price creeping back up.
The GTX 480 or GTX 570 or R7850 will run all current games on ultra/max settings 1920x1080 so it really doesn't mattter which one you get unless heat and power are an issue and your gaming on a higher res.Depending on which games you intend to play, one will perform better than the others.