I use selenese runner to run selenium commands against a browser - usually phantomjs. Really depends on how complex you want to do. Scripting something like phantomjs directly would give you some more flexibility.

"Right tool for the job" gets bandied about way too much, when the reality I see too often is that most developers making these decisions don't know how to choose a 'right tool'. They usually don't have enough experience with different technologies not enough understanding about the requirements to make a good choice. Another aspect is team - the "right tool" for a .NET shop that needs to get out a stable and long-lived tool is probably .NET, not the latest/greatest tech that one intern raves about after hitting a local tech meetup. I've also known way too many devs practice resume-driven-development, choosing new/flashy tech primarily so they can learn it, but justifying the decision with benchmarks and other fluff. To some degree I've been guilty of this myself in years gone by, but have been involved in too many maintenance projects to see the downsides of this.