The first thing i would mention is eye protection. I wear glasses, but i also wear cocoons over them for extra protection, these wrap all the way around. I know a couple of master casting instructors that have had VERY close calls, so if it can happen to them it can happen to anyone.
This 'myth' that talks about barbless flies loosing fish is quite bizarre, i often hear it from the older generation of UK anglers and i think it comes from spinner and lure fishing for salmon. As i'm sure you know, one of the reasons a tube fly slides out of the way when you hook a fish is to prevent the fish from levering the hook out, as these tubes can weigh quite a lot. Lures are also quite weighty, and you can loose fish if these aren't barbed. Flies for still water trout especially don't weigh that much, so theres no need to fish with barbs, even a dog nobbler.
When i used to fish for salmon and sea trout 'tup north' on the Wear, i never fished barbed flies, and i think i only lost 1 fish all season.Advantages?
1. I think barbless flies give you a fantastic hook set as you don't have to overcome the increased surface area of the barb (all else being equal), try it with an old cloth with a barbed and de barbed fly. The de barbed fly will go in much easier
2. less injury to the fish, especially if you accidentally foul hook the poor thing
3. Safer for you, your equipment, and others. I have hooked my finger whilst tying on a fly and accidentally tripping over the leader. Trying to take out a barbed fly isn't worth thinking about.
4. if you keep tension, you are highly unlikely to loose the fish, unless it's not a good hook set, but the lack of a barb gives you one anyway
Disadvantages?
1. If you tie your own flies, a barbed hook might cost you more
All the best and tight lines
Nick
