If the X300 has a 128-bit memory interface it's probably a bit better; if it has a 64-bit memory interface (X300LE or X300SE) it's probably a bit worse.
Either way, the X300 is probably better overclocked. Tell him to go to town.
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<b>Radeon <font color=red>9700 PRO</b></font color=red> <i>(o/c 329/337)</i>
<b>AthlonXP <font color=red>~2750+</b></font color=red> <i>(2400+ @ 2208 Mhz)</i>
<b>3dMark03: <font color=red>4,876</b>