Virginia is a more valuable asset to the SEC than Virginia Tech.
However, the HOME RUN for the SEC, given everything that's been mentioned, is without a doubt the value that UNC would bring to the SEC. Flagship school in a 9M population state that is growing, top 10 basketball program, high ceiling football program with the SEC label on the uniform, national brand and following, geographic and cultural fit, solid academics, etc.
V Tech and NC State would be like adding another Mississippi State and Auburn.
I also think UNC or Virginia would be more likely to join the SEC, if the other school is coming. Both are flagship schools of their respective States are would fill out the SEC from a geographical standpoint.
I am surprised to see FSU and Clemson still being mentioned. I think the likelihood of that would be less 1%. The SEC already dominates the Florida and South Carolina markets. They would add much less to the conference than the UNC and Virginia scenario.