We'll start with CPU performance then move into the GPU later. With the CPU, the most important comparisons are between the Core i7-8705G and Intel's previous and current generation H-series CPUs, in particular the Core i7-7700HQ and the Core i7-8750H. Both are 45W CPUs, similar to the power available to the 8705G's CPU; the 7700HQ has the same four cores, while the newer 8750H bumps it up to 6 cores.
Looking at Cinebench R15 we can see that in the multi-threaded test, the 8705G holds a decent 8 percent performance advantage over the 7700HQ, using its higher clocked cores to its advantage. In the single-threaded test it pushes this margin out to 13 percent, again thanks to better boost clocks. However it's in the multithreaded test that the 6-core 8750H dominates as expected; with two extra cores, the Coffee Lake CPU is 46 percent faster.
It's a similar story in the Handbrake x265 encoding test. The 8705G is a mere 2 percent faster than the 7700HQ, but gets punished to the tune of 27 percent against the 8750H. Having those extra cores in Intel's newer H-series CPUs really helps in these intensive encoding tests, whereas Kaby Lake G appears to be stuck with last-gen CPU technology.
In Microsoft Excel, the 8705G is 3 percent faster than the 7700HQ, but falls 33 percent behind the 8750H. Again, this is down to the 8750H having more cores, which is a large advantage in most modern multi-threaded workloads.
The 8705G does hold a handy performance advantage in 7-Zip's compression and decompression benchmarks, to the tune of 13 and 8 percent respectively. However once again, the 8750H comes in and smashes the 8705G, achieving 38 and 57 percent more performance in these tests. There's a pretty clear trend here, and it's not one that favors Kaby Lake G over Coffee Lake H.
In mixed workloads we start to get a good look at how the CPU and GPU combination stacks up. When accelerating a Premiere encode with Lumetri effects, the 8705G competes strongly with gaming laptops that pack faster GPUs. The combination of a 7700HQ and GTX 1060 is not seen in slim and light notebooks like the Dell XPS 15 2-in-1, yet Kaby Lake G is only 20 percent slower here.
Across most CPU limited workloads though, there's a pretty clear trend. The 8705G is marginally ahead of the Core i7-7700HQ thanks to its slightly increased clock speeds, but it lacks those extra cores of the 8750H. As such, the 8750H is often at least 40 percent faster in crucial workloads like video rendering.