A different R/X ratio means the transformers have different resistances or reactances even though the total impedance magnitudes are equal. The phase angles of the two impedances will be different.
When current flows, the voltage drop through each transformer's impedance will cause a slightly different phase shift so the output voltage vectors will not match and circulating currents will flow.
To illustrate, imagine two transformers each with 1 ohm impedance, but one is all reactive, 1 ohm @ 90 degrees, and the other is all resistive 1 ohm at 0 degrees. Run 100 amps 1.0 pf, through each transformer and the voltage drops will be 100V at -90 degrees and 100 V at 180 degrees.
If all else is the same, the transformers output voltages will be off by 141 volts. That voltage difference will cause circulating currents to flow between the two transformers.
If you have the specific data on each transformer and a rough idea of the load, including power factor, you could calculate the circulating currents and see if that particular match was a problem.
