One thing that isn't fair to these old derailer's makers is to judge their shifting performance using flexible, modern chain.

Even Suntour's and Shimano's chain gaps were pretty huge back then, especially on touring models like the V-GT and Tourney GS.
But it mattered much less when we were all using traditional "bushed" chains that had so much less lateral flex.
So, when using modern chain on my vintage bikes, I'll often figure out some way to reduce the chain gap, by either adjusting the spring tension balance between the cage pivot and mounting pivot (typically Shimano, Simplex or Gran Turismo), or by removing the B-tension screw or even grinding metal from the locating lug where the B-tension screw used to be (Suntour).
All of the above in addition to fine-tuning the chain length and axle position (with derailers having an cage pivot offset from the guide pulley).

I give the Allvit high marks for it's clever, inverted, "knee-action" tracking of the freewheel's outer profile, especially as it's design traces back to the late 1950's.