Im Curious about this as well. I do know a virtual texture material has additional texture fetching per uv set. But multiple textures can share the same uv set… so if u have 3 textures that use uv0… they have an additional texture pass… which makes it 4 texture fetches. If you have a 2nd uv set… it will again add an additional texture fetch. If its just 1 texture u will still have 2 texture fetches… With traditional textures its just 1. Also some additional math … multiplies … adds … etc… under the hood for virtual textures.
That being said im curious about the draw call limiting. Nanite batches draw calls incredibly well, but the idea of making it even better by putting it all on 1 large texture atlas could potentionally make 100 draw calls 1 draw call.
Virtual textures seem great for landscape… additional memory price, but cheaper to render landscape material since its way less texture fetches overall… instead of 4 texture sets … its just the 1 texture with 1 additional fetch for the uv…