The end result of many testing Valla’s Bequest is that it has some wonky interaction with strafe’s frames. Since Strafe’s frames are already all over the place, it is believed that the pierced strafe’s projectile (not the generator shot by it) may produce another generator. This theory was really hard to replicate, but it has happened.
What we do know is that the strafe’s % damage on Valla’s Bequest as well as it’s pierce has no effect on GoD6’s generator shots from strafe. This has been proven in videos in clips from various streams, as well as my own.
The same goes for Buriza. Buriza however has a higher base damage, and since attack speed has no effect on strafed generators, then technically a 2hxbox will naturally deal more damage if you wear it.
Bringing extremely high paragon clears into the mix makes it a little wonky because usually those guys have enough keys to get a dream rift (festering, missile dampening dragging, conduit, power pylons) and Flavor of Time on those dream rifts really skew results as that becomes more important than the actual build you are running at that point.