[PL_Andrev]

The advantage of model 9500 card is the only one: is very cheap (hmmm... and more silent).

I compare Gigabyte cards 9500GT and 9800GT with 512MB RAM DDR3 both:

Efficiency of 9800GT is two-three times better than 9500GT with results:
3D Mark: 2x more than 9500GT
GPU score: 3x more than 9500GT

On hi-res games:
9800GT has 2x better result with FPS (no FSAA/no AF)
... and 2x / 3x better result with FPS (FSAA/AF)
2x for high res more than 1680x1050 / 3x for 1280x1024

PT Boats: Knight of the Sea 1280x1024
FSAA 4x / AF 16x:
9500GT - 11.7 FPS
9800GT - 28.6 FPS

(all data: non-english source)

Summary:
On my market 9800GT is only 1.5 more expensive than 9500GT.
But 9800GT is 2x / 3x more efficient than 9500GT.

So, this is reason than 9800GT is better than 9500GT (Gigabyte with 512MB both)

* * *

When I compare RAM (DDR3), card with 1024MB is only 10-20% more efficient than this same model with 512MB (but I think that it depends from game requirements and code's optimalization - SH5 bases on SH4 engine, so it will be small profit form 1MB card)