How do they compare? Which is better for tempos/road races?
I've run tempos/road races (even a few XC races) in the LunaRacer since they first came out. I haven't tried v4, but I didn't love the upper on v3. And I've never tried the Streak.
Additional info: I'm training for the half. PRs: 14:50 5k, 30:30 10k. One bonus to the LunRacer is I get 500+ miles out of a pair, and it's enough cushion I feel comfortably doing 14 mile training runs (usually including 10 miles of tempo). If the Streak can't do that, I'd probably continue leaning towards the LunaRacer.