I think that developing "advanced" weapons in isolation would be an exercise in futility. If there's a race that's experienced in interstellar war out there, their weapons would be much more refined than ours. You can't create any product independent of its context.

If we were to meet a hostile alien race, unless they were at a similar developmental stage (which seems unlikely), we'd be at their mercy either way due to the extent of the other side's settlements.