AMD cards that are BIOS modded definitely use oldkernels
AMD cards that are overclocked right on the edge might need oldkernels

Go ahead and try new kernels. With everything the same as before. If theres any instability or increase in rejected/incorrect do not bother underclocking just go straight to oldkernels.

The main difference between the two I've found is you don't get the fluctuating hash rate with the newer ones.  So if you can get away using them do it.

That's my story and I am sticking to it.