I’ve tried all kinds of net retractors, from the clip-on type to the magnetic ones. My favorite one is from Orvis (more info here).
It is lightweight and pulls out very easily. I like how it’s easy to decouple the net from the cord, making it easier to take a photo of a fish, or to wedge the net in some rocks to let a trout revive at its own pace. Also, the cord retracts smoothly and easily, so I don’t have to worry about clipping back on the net or making sure that the magnetic ends reconnect.
I’ve also moved from a mesh net to a lightweight rubber one. The one I use now is a 13″ x 18″ Frabill net.
They’re cheap and really hold well the fish. I found that mesh nets really got tangled with my nymphing rigs, and, sometimes, dug into a fish’s gills. The rubber nets do a good job of cradling a trout.