Radeon 32meg SDR. Faster in virtually any 32bit benchmark over the the MX at higher resolutions. Superior 2d and video capability but doesn't have twin view. So maybe it depends on what you want to do with your video card. Here are some reviews in comparing them, most are relatively old but maybe useful.
<A HREF="http://www.rage3d.com/reviews/hardware/radeonsdr/" target="_new">http://www.rage3d.com/reviews/hardware/radeonsdr/</A>
<A HREF="http://www.tomshardware.com/graphic/00q4/001019/index.html" target="_new">http://www.tomshardware.com/graphic/00q4/001019/index.html</A>
<A HREF="http://www1.anandtech.com/showdoc.html?i=1334&p=1" target="_new">http://www1.anandtech.com/showdoc.html?i=1334&p=1</A>
<A HREF="http://www.sharkyextreme.com/hardware/articles/ati_radeon_32mb_sdr/" target="_new">http://www.sharkyextreme.com/hardware/articles/ati_radeon_32mb_sdr/</A>
Radeon drivers have improved significantly from October when most of these reviews where conducted. Radeon W2k is just as fast or faster then Win9x in everything except Directx stuff (pretty significant). So if you are a Win2K person solely or a linux user then get a MX. If you are a gamer and using Win9x and not planning on using linux or solely Win2K then consider the Radeon SDR. Also consider the Radeon LE which is a 32meg DDR board which when configured right outperforms the Radeon SDR and MX on virtually everything for less then $90 delivered to your door if you live in the states.