An FPGA isn't any better at accuracy than a software-based emulator.
Accuracy is all about understanding the original hardware. WinUAE matches the current level understanding of the platform, minimig (open FPGA core) does not.
Hardware definitely is harder than software, so FPGA is harder if anything.
... and yet I still prefer hardware. Latency and jitter relative to the target platform is a serious issue with software.
Current computers just aren't made like they used to, and popular operating systems outright suck at guaranteeing latency.
(And the market agrees, else everyone would be selling amigas for 100 bucks.)
And real hardware? Original hardware? Slowly it gets damaged, dies, breaks, and so it becomes a rarer commodity.