Takeaways
Output :
V1 has higher peak output. 4/10 stop is considerable especially considering the FJ80 is a bit bulkier of a light.
When you adjust recycle and FDA specs for peak output, the V1 closes the gap where it is "outperformed" on a specs sheets.
Meaning, if you drop the V1 to 1/2 +.6 power to match the FJ80's output at full power, it recycles in the same time (1.2s), and it's T.1 FDA is about equal.
The V1 has a larger and more consistent output range.
Flash Duration :
The FJ80 has superior FDA's at higher power level (without adjusting for it's lower output).
The V1 surpasses the FJ80's T.1 Flash durations between 1/8 and 1/16. By low power settings (1/64-1/256), the V1 significantly distances itself from the FJ80, with an FDA that is half the duration.
While the difference is significant, I don't think this matters much. Neither of these strobes are ideal for freezing motion as they offer such low output.
Color:
The Westcott has a much more pleasing white balance (significantly closer to 5600K daylight).
The Westcott has less tint / is closer to neutral white.
a ".3M" CC# rating means a CC30M Magenta filter would offset the light's green cast. So the higher the number, the more green the light is. Conversely .3G would mean the light has a magenta cast and requires a green filter to neutralize. The V1 has more of a green cast throughout a majority of it's power levels.
The V1's white balance is concerningly cool. After all, this test was done in a double diffused softbox which tends to add warmth to the light. So if you've been using the V1 as a key light and feel as though your shadows look warm/magenta in your global-adjusted images, this would explain why.
Other:
If you are planning to cross-reference either of these lights to the other Westcott vs. Godox datasets I've published, keep in mind this test of the FJ80 / V1 was done at 30" whereas the other strobes were done at 60". This was necessary to report accurate values at low output levels. This means in order to compare output information, you would need to decrease the above output figures by two stops.