Even regular glass varies in spectral transmission so it's hard to say. But I'm pretty sure polycarbonate has better light transmission characteristics than the typical glass used in aquaria and their covers.
But better is a tough term to pin down here. What's better in one application is not necessarily better in another. I know of one zoo who has a large dome built over an indoor rainforest. They have some panels designed to transmit UV light for certain animal species. They are strategically placed so these species can bask. Interestingly enough, the animals are more likely to bask underneath a panel that transmits UV than a panel which is not.
But the plants surround those areas tend to suffer burns and die off. So "better" is a relative term. In this case what is better for the animals is not necessarily better for the plants.
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Current snakes:
0.0.1 Gonyosoma oxycephala - Java locale (green)
2.2 Gonyosoma janseni - Seleyar locale (all black)