Especially around the holidays, one shouldn't try (even if it would be allowed) to do standby in a way that could strand one without a seat. Standby to an earlier flight is find, even if it potentially just means more time at the connecting point if the next segment doesn't clear, but not to something later.

An advantage of buying the new ticket on a different airline is that OP could potentially get a full refund if the flight is rescheduled, cancelled, or significantly delayed. Some people here might also hope/try for a VDB on it, but of course that would require checking in and being at the gate, with some airlines now denying comp if you don't take the new flight they give you.