To state the obvious...the strength of the beat makes a big difference. With cassette tape as weft, the obvious becomes even more obvious.
You can see I lost about 30% beating firmly and consistently on the right vs. beating lightly and somewhat lackadaisically on the left.
The cassette tape as weft looks cleaner and better executed with a firmer beat. The lighter beat has a more organic and unfinished look. The firmer the beat - the less obvious the actual nature of the weft. With a loom allowing even a firmer beat I suspect the results would be even cleaner and the cassette tape would resemble thin yarn until you touch it.
Note to self: the firmer the beat...also the less crackling sound.