Decoding speed is really not an issue with FLAC on any modern CPU. Period.
You are FAR more likely to be bottlenecked by the source storage, unless it is a SSD or ultra-fast array.
NOTE: If you look at that PDF in the Test Setup, he's using an AMD A4-3400, which was a low-end, ~$60, dual-core, AMD Llano part designed for ultralights and netbooks, introduced in September 2011. And, his charts are only showing percentage utilization of a single CPU core.
A A4-3400 gets absolutely BLOWN AWAY by even the lowest-end Core i3 now. Even then, because AMD has been struggling for years since Intel switched to the Core architecture and Tick-Tock.
So... Differences are pretty exaggerated in that.