Liam,
A CDC fly, as is true for a Para pattern, can mean different things to different people
Here's my take on things;
If you require a fly tied on a Klinkhamer hook be it a CDC emerger or standard para type fly,
I know of no hooks which are barbless, which is not an issue as there are more micro barbed flies on the go now OR you can simply flatten the barb OR both.
If you require a fly tied on an emerger style hook, again be it with CDC or Para style hackling then, again of the 5 types that I can think of they all have barbs, albeit 4 types are micro barbs and the above will again apply.
If you require a barbless hook for on the surface then the Partridge SLD is hard to beat, this is an area which has a reasonable selection of barbless hook types & I think that the SLD is as good as any. Dan indicates the Tiemco 103BL and this hook is a lovely looking light bit of engineering and has a very wide following but I've had 4 or 5 straighten on me and that's why I've a good few in a box that are gathering dust, straightening out on a Rainbow is one thing but on a decent Brown in the river can make a grown man cry.
I've never had an issue with Tiemco 900BL's either, a good solid hook.
I rather like the Tiemco 102Y's but again these are micro barbed and that wasn't your original question.
Dohiku HDD 301's are quoted as Dry fly hooks but although I have used them without issue for F-Flies, the shank length to gape ratio just looks....untraditional?? Good hook though.
The varivas 2120WB I liked the look of but again I've no confidence in them after a straightening out incident.
Nymph hooks - I can only personally see a couple of avenues. As most of my nymphs are bottom dwellers I like the traditional long heavy hook like the Mustad R72, which I can't get locally now but this is no issue as they were barbed and I have now found the Tiemco 3761SP BL, which I think is an excellent hook - anyone any thoughts on the spear point design?
The Partridge Ideal Nymph comes in micro barbed and barbless, these are what I'd consider dodgy in larger sizes & waters with larger fish, never held much confidence in long shanked hooks with such relatively fine wire..............maybe it's just me.
Listen to every reply and the various experiences with different models and make an informed decision 'cos remember hooks are expensive, I saw a packet of trout hooks (25 pieces) for pennies under £6 last week
find a type per application and stick with them.
Iain