I personally chose RADV after looking into this myself and the only drawback from my understanding is that they are proprietary drivers.
RADV is the open-source community developed Vulkan driver. It has the widest hardware support of the three Vulkan drivers and is generally the best for gaming.
AMD provides two more Vulkan drivers - AMDVLK is the open-source one available in AMDGPU, then there’s the unnamed proprietary Vulkan driver in AMDGPU-PRO. The biggest advantage of the proprietary one is that it is certified - doesn’t matter most of the time, but when it does, a missing certification is a deal breaker.
I really don’t think that’s the case, assuming you’re talking about AMDVLK (amdgpu is the kernel module used by all three Vulkan drivers - RADV, AMDVLK and the Vulkan driver from AMDGPU-PRO). Ubuntu and Fedora definitely default to RADV, and Arch Wiki recommends RADV unless you need something from the other drivers.
NixOS seems to default to RADV according to their Wiki. If this was a few years ago then maybe you might be confusing it with the ACO shader compiler for RADV? That brought a significant performance increase and eventually became the default in RADV. I remember using custom Mesa (the project that develops open source graphics drivers, like RADV and radeonsi) builds to massively reduce stuttering in DirectX games.