Is there a full list of the differences between the graal jit and C2? I was only aware of graal having better partial escape analysis over C2's conservative EA.

It's simply a completely different implementation. Some of the optimiization passes are the same, obviously, but overall it simply performs ... differently.

But inlining will not cause better performance in every case, will it?

Correct! Inlining obviously costs CPU, code cache space, and makes the receiver method bigger so that it's less likely it will be inlined itself. If there ever is a decompilation occuring, the inlining efforts were pretty much wasted.

However it must be pointed out that inlining enables further optimisations.

The tradeoffs are more complicated for a jit, but for an aot compiler it’s one of the most important optimisations in the pipeline.