PEFV is the old way of doing it (legacy), the LIC-VIA is the new way which was introduced I think in ArubaOS 8.2 or 8.1.
Today, both models are still available and you can select either where the PEFV gives most value if you have a lot of concurrent users on a controller or if you run ArubaOS 6.x. LIC-VIA is better for future deployments and if you want to start small or stay small on concurrent VIA users, and it works for virtual controllers as well. It might be that the LIC-PEFV will go end of sales somewhere in the future.
In short: go for LIC-VIA, unless you have good reasons to get PEFV.