V9FS and FUSE both enable userspace filesystem drivers. They are actually pretty interchangeable for 99% of use cases, and the rest of those cases are where you'd directly interact with both, so it wouldn't be fair to compare a FUSE library abstraction with V9FS.
FUSE is too complicated to directly interact with, so everyone (OP included) is using libraries and abstractions on top of it. So what you'd really be comparing is that abstraction, as well as possibly how it limits actual FUSE interaction. Additionally, the performance of these abstractions is hard to predict, as many do lots of work (threads/IPC/etc) silently in the background, so the apparent workload on your filesystem driver is far from actual workload.
V9FS is simple enough that drivers often just talk it directly. The protocol is a simple RPC mechanism, and parallelism happens naturally.
As far as a direct comparison example, I don't know of one.
FUSE is too complicated to directly interact with, so everyone (OP included) is using libraries and abstractions on top of it. So what you'd really be comparing is that abstraction, as well as possibly how it limits actual FUSE interaction. Additionally, the performance of these abstractions is hard to predict, as many do lots of work (threads/IPC/etc) silently in the background, so the apparent workload on your filesystem driver is far from actual workload.
V9FS is simple enough that drivers often just talk it directly. The protocol is a simple RPC mechanism, and parallelism happens naturally.
As far as a direct comparison example, I don't know of one.