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.