They have the same meaning. However, til(l) (spell til(l) without the preceding apostrophe. On contrary, it is regarded as wrong) is generally considered less formal, and it should not be used in writing. Also, don't start sentences with til(l).
Until is more often in both speech and writing.
One more thing: Don't consider til(l) as an abbreviation for until. Til is way older than until.
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