You're asking whether an assignment then a possible re-assignment is 'better' than an if-then-else with a single assignment. Yes?

My question to you (building on another AM's) is what your criteria is? Is it readability and maintainability? Or, is it speed? In this trivial case, speed is pretty much a wash. Were you to be doing multiple assignments, however, it might be better to use A than B. In either case, the difference in CPU time per branch is minimal and not a factor.

As a coder who more often than not gets down to assembly, I'm used to B, and I think most coders are. As long as you don't need to make a flowchart for Management, B is every bit as usable as A from the maintainability standpoint.