Your chances of garnering the dreaded SSSS, which positions you for a most certain secondary look-see (wanding, pat-down), are vastly increased when booking one-way tickets. It's not a 100% guarantee but the probability is quite high. If the additional security entailed in your journey doesn't bother you, then flip a coin. If you want your chances increased of being left alone by the TSA, then book the open jaw.
Just MHO.
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essxjay
FT Travel Safety/Security moderator