Within the limits of accuracy of the binning, these both have the same Vf,
but the SXOH is rated at 350mA while the TXOH is rated at 700mA. So if you run both at 400mA the SXOH will produce just over its "S" bin output, while the TXOH will produce under its "T" bin rating. The SXOH will be brighter. See DFiorentino's recent post for hard data from a few LED examples he has tested. It's here: http://candlepowerforums.com/vb/showthread.php?t=120454&highlight=difiorentino
