I have used nvdia cards from tnt upwards to a geforce 4ti4200, currently using a geforce 3 as my geforce 4 died :-(. Performance is very good as the opengl drivers are superb. Never used an ati card yet (128mb 9500 on the way) but their drivers are improving in this area according to review on techreport / aceshardware. Answer is in my opinion go for a ti4200 128mb, cheap price good performance.
Note - the above is really only relavant for 3d modelling, as mentioned 2d is less taxing on vid card - more memory would be a better bet.