If a graphic card has DDR VRAM insetad of SD VRAM of course it wil be better and faster
Erm, not quite. For example, the GF2 MX 400 had:
SDR running on a 128bit bus
Wheras
The GF2 MX200 *which was a lot worse* had:
DDR running on a 64bit bus
As DDR has a higher latency than SDR, the card proved to be somewhat slower than it's SDR equivalent which had the better bus.
I don't believe the same limitations exist on the GF4 MX line, but it could be worth you checking Nvidias site just to make sure.