Really, it's going to depend strongly on the tape head, and on the length of the cable. For high-inductance heads (over, say 300mH) capacitance is usually your enemy - it resonates with the head's inductance, and no exotic material is going to make up for excess capacitance.
For very low inductance heads (usually they will have a step-up transformer at the preamp end, unless it is an exotic current-source head) you must worry about magnetic field hum, so shielded twisted pair and a differential input is going to work best; capacitance is not the problem here.
In the middle range, say 100mH to 300mH, you will want to worry about both problems. I'd take shielded twisted pair for preference even with an unbalanced input, though coax can work equally well if carefully implemented. For runs longer than 1 meter, capacitance is again the main problem. Use short runs!!