Well, ya can't say performance, because much of the software doesn't take full use of it, nor parallel threads.
In fact, big-little configurations are mostly big baloney configurations! Many compute programs, or even games, refuse to use the big (performance) cores, because they generate too much heat, and instead run them at lower or half speed loads, or nothing at all (just the little cores).
Power consumption at 1watt for performance cores vs 0.5W for little cores, makes very little difference as well.
Idle power consumption is all in the milli-micro Watts, or cores are completely deactivated, using zero microwatts.
So what would I buy them for?
Probably graphics performance is the only thing, and even that, games like robot wars, CSR or asphalt, aren't able to fully utilize the GPU of high end smart phones.
So I would go for mid-range CPUs, like a modern SD 600 series, based on cost.
CPUs for $200 phones or up, aren't the limiting factor of a phone anymore (unless you get Chinese phones with Kirin CPUs, they both suck in performance and power consumption).
I would divert your attention to make sure the phone has at least 80 available gigabytes of disk space, 6GB of RAM (doesn't matter if it's a bit slower ram), and most prominently battery life and longevity.
The last one, longevity rules out pretty much all Chinese phones, as their batteries tend to last for about 1 year before losing 25 to 50% of it's new life.
Phones like Google pixel, iPhone, essential phone, and even LG and Samsung, their batteries outlast their phone's useful lifetime.
Aside from that, you'll may want a phone with good reception, both cellular as wifi, and function on your network speed (quite often 10mbits is about all you really need, but some can do with 3 to 5 mbits).