Re: Any casting differences between WF and DT lines?
As far as ease of casting the same weight line in either type, it would more likely depend on the fly you're trying to cast, the length of the cast & the wind conditions, and assuming that the leader & tippet combination you're using is correct. Really too many variables to say one way or the other, and would more depend on the factors involved. In specific situations & conditions, one may be better than the other, that's why they make both types. Neither may be ideal for all situations however, so what you choose, will always be a compromise, but should be selected for the majority of the fishing situations you'll see & the majority of the conditions you'll likely encounter.
For example, if you're primarily a dry fly trout angler, you may find the DT line to work best for you, but might want to also have a WF line if you sometimes use streamers. Either line type could be used for both, again depending on the variables I previously mentioned.
Myself, because I'm primarily a bass & saltwater angler, all my lines are WF's.