Most of the times I've looked at it, ARM still seems to be lagging behind x86 a bit, but the gap is much smaller than it used to be. For example: https://news.ycombinator.com/item?id=41925983

Of course the specifics will depend on what you're doing: for certain applications or code-paths ARM may well have 100% parity, or perhaps even have more optimisations than x86.