Keith Elder has what I think is a nice analogy of the difference between ASMX web services and WCF services:
This question comes up a lot in conversations I have with developers.
“Why would I want to switch to ASMX services?”
One analogy I have come up with to explain the difference between the two is an airplane analogy.
I associate ASMX services with a Cessna 150 cockpit and I associate WCF services with a 747 Jumbo Jet cockpit.
See the full post for great compare and contrast photos, as well as the full argument.
I don’t agree 100% with his conclusion, which seems to weigh heavily in favor of WCF. In my opinion, there are times when a Cessna 150 is just what you need, and the same is true of ASMX. But I think he’s absolutely right when he notes that the reward for learning the complexities of WCF configuration is a much more powerful and flexible tool for providing and hosting services.