I think custom kernels can do some great things but I don't usually run them for straight performance gains.
I care about overall optimizations and usually the stock kernels are pretty good at that. You get a good mix of battery life and performance. Custom kernels tend to be more purpose built and many of their strengths are at the expense of others things.
I use Franco's kernel on my Gnex and I keep it close to the stock settings because that's really a good balance. What I care more about are all the color and sound hacks he's added into the kernel. It really makes the screen pop compared to the washed out look it has when it's stock.
Quad scores are fine I guess, but I don't think they are a good indicator of the ROM/Kernel's daily use performance. I've seen plenty of ROMs and kernels hit very high on benchmark scores but they didn't feel faster than other ROMs and kernels.
A good example of this my transformer prime, I got stupid high numbers on that, much higher than anything the Nexus 7 but it's WAY slower for day to day use.
Its about balancing things out for the best overall experience I think. But that could just be me.
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