word of warning
many people run around saying just oc that Ti 200 to Ti500 speeds.
the ti 500 uses different PCBs which increase stability at high memory speeds
those that get the Ti 200 to Ti 500 speeds are very lucky and in the 10%
as far as differences between companies: very little
Leadtek claims that the voltage on thier cards are more stable, they have special name for it
some use different coolers then others
i do not like the Leadtek coolers since they have those GPU and memory cooler in one huge sink
the heat from the GPU might heatup the ram more this way.... MIGHT
id suggest buying form a different company Gainward or Visiontek are both great.
pretty much a Geforce card is a Geforce card
they all follow the refrence design closely, for the most part