For opening apps and documents, and searching the Web, any of these launchers will get the job done. Although Spotlight's preview feature is handy, it's less powerful and flexible than the dedicated launchers when it comes to other tasks.
Of this batch, LaunchBar is the most approachable and requires the least configuration, with Alfred coming in as a close second (but only with the optional Powerpack, which adds features such as iTunes controls, email searching, a clipboard history, and workflows). But if you already use — and love — a different launcher, the transition to a new one may seem awkward and unnatural. There are no bad choices, here, as long as they work for you.
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