Direct association may be possible. It requires that both of the switches in the virtual three-way be zwave and be relatively close to each other, and that the auxiliary (which will be the trigger) support association.
A direct association will work even if The hub itself is not working, or if the Internet is not available.
it will probably be a little faster than going through the hub, but to be honest not that much faster if you have an efficient zwave network and you are using the local features of smartlighting… Humans might not be able to perceive the difference.
There’s no way to set filters or modifications on the operation of the virtual three-way if you use direct association. It’s going to be just like a wired three-way in that sense. Every time you turn on the auxiliary, the master will come on. That’s probably fine for a three-way set up in the same room. People do sometimes use virtual three ways using the hub method when they want light levels to be different at different times of day, for example so that pressing the auxiliary between midnight and sunrise only turns the light on to 50%.
Not all direct association devices will update the hub when the state changes, which means the hub may think the lights are off when they are actually on or vice versa. Direct association is an older method which was used before people had smart phones for everything, so they didn’t care that much about the hub knowing what the state was. But now people expect to see it. This varies from model to model and it’s rarely documented, so sometimes you just have to try it and see. In contrast, the methods which go through the hub will update the state because obviously the hub knows what’s going on.
In general, I think direct association is a good choice for zwave virtual three ways. I especially like the fact that they work even if the hub is down. But I understand the advantages of being able to control events with filters, too, so it’s a personal choice.
On the other hand, I no longer usually recommend zwave direct association for “motion sensor turns on the light” or “contact sensor turns on a siren” which were some of the original use cases for the method when it was first introduced, because nowadays I think people are just much more likely to want to have filters on those.