This is a bit of a false dichotomy, as even the languages in A tend to become used in the form of B. I like Lisp, but I use Common Lisp, not Lisp 1.5. The only example of a pure A language I'm familiar with and also commonly use in that form would be APL, although Forth also counts.
The languages of A have their purposes, be that experimentation or innovation, but I don't think B languages should be criticized. Ada is a nice B language, designed over years collecting requirements, appropriately for the US military.
It's a bit of a non-answer, but I use these two different types of languages about evenly. I tend to be able to expect new thoughts and ideas from A, and more practicality from B, although I don't learn a language unless I expect it to teach me something that will change my ideas of programming.