When I was a kid, our fishing net was aluminum with a moss green cotton bag, the kind you buy from the local Hardware. We landed a lot of fish from Otter Lake with that thing. It was a reliable companion, full of memories and always willing to go fishing no matter the weather.
The bag on the net bellow is injection molded PVC , there is some thinking that the rubber type bags are easier on fish. I don't know for sure but they seem practical and easy to use. Wachter nets use beautiful woods and the latest technology in their design.
Fishnat produce a line of nets with all rubber bags that look good. They claim that it is a better bag for catch and release.