Which one can`t decide Nvidia or Ati?

Hi all i need help!! Pleeeeeezz! I have a Nvidia Geforce 7300le 512mb and i have just decided that i want to play Crysis, Ghost etc but i want to run Crysis on full settings and i have heard the Nvidia 8800GTS will do it but i have seen an Ati Radeon HD3780 fro around the same price and noticed that the Nvidia has 128 stream processors and the Ati has 320 but does the Ati use DX10 or what i like Nvidia as i have had no problems with them but i used to ues Ati which is better i need someone who is into gaming any ideas?

Also i have Q6600 CPU and 4GB Ram so not worried about Game speed.