What specifications matter when comparing TVS ICs?
If you look at a parametric search for TVS diodes, you will see columns of the parameters that differentiate the diodes.

The most important are breakdown and clamping voltage, peak pulse power/current, and whether the device is bidirectional.  Bidirectional diodes are back to back diodes so that they can clamp both positive and negative voltages.  For high speed digital lines, the capacitance is also very important, since high capacitance will attenuate your digital signals.  

If you choose a diode with similar breakdown/clamping voltages, peak pulse power/current, "bi-directionality", and capacitance, you should be OK.