In open source vhost is a pretty good option that abstracts hardware away from VMs and generally performs well.

That said, SR-IOV isn't a BAD option if you don't care about live migration of VMs over a lifespan potentially longer than the underlying hardware platform. It's a good option if you can live with host-hardware-specific drivers in your guests, you're willing to standardize on a specific NIC as host hardware for the fleet where you'll be running VMs, and you're willing to deal with the resource commitment it requires to deliver on its performance promises.