This makes them very different and is usually why you can squeeze more out of a console than a PC of equivalent specs.

That's not why. The reason why you see a console performing better than a similar PC (as in, both CPU and GPU being similar) is that consoles use more efficient, low-level APIs. That's especially important for the graphics API, since graphics is just about the most demanding thing a console (or PC) does, and a low-level API puts a lower load on the CPU to achieve the same results. So while PC and console GPUs perform the same, console CPUs actually have an advantage.

The shared RAM isn't a benefit in any way whatsoever. It's the opposite, it's a drawback that consoles have to deal with because, unlike PCs, they only have a single memory controller. PC CPUs and GPUs ecah have their own memory controllers, so they can have their separate memory pools, with the CPU using DDR for low latency (since it doesn't need much bandwidth) and the GPU using GDDR for high bandwidth (since it's a highly parallel processor that doesn't care much about latency). Consoles don't have that option, meaning they must either use a single pool of DDR and hurt the GPU with low bandwidth, or a single pool of GDDR and hurt the CPU with low latency. They go with GDDR because the impact of the CPU is lower than the impact of DDR for the GPU would be.

There is no context in which shared memory between the CPU and GPU is better than having their separate, specialized pools.