Neither shoe really matters for a half, Mo just ran a 59:1x half marathon in spikes
Nice. Why don't you wear spikes for your next Half then?
Ignoring the faster recovery the VFs allow, I would probably run just as fast in Zoom Streaks. They are really built for the marathon. The Alphaflys have another 1oz of foam cushioning packed in so they make even less sense for a shorter race.
The streaks are not anywhere near as fast as VF. I've worn both for a races between 5k and half marathon. The streak is still a good shoe but it is no VF. Jakob used the Alphafly in that road 5k he ran and he was very fast for the last K. He held back a lot through most of the race.
Not my experience but whatever. The point is the VF, and moreso the AF are primarily marathon shoes, so a runner's choice at a shorter distance doesn't indicate which is better for the marathon.