I'm not a specialist on the subject but IMHO ATI is the best of the two as it is an All-In-Wonder card, which includes a TV tuner...

Hello,
Nvidia has best cards but its to expensive, ATI make very nice card for low prices (the HD3850 for example)

ATI or NVidia are equals...

There's goods products in both constructors...

To choose a card the first thinking is the price ! ;)

After comes the mark (asus, gigabytes, sapphire...), (don't buy "no names" : wrongs drivers, bad warranties...)...

And above all, wich MB do you have, wich slot (AGP or PCI Express), is your MB older than 4 years, what kind of power supply do you have...

So to get a good agp card (ati or nvidia), first look at your processor kind, your ram...

If you've got a 2400+ amd & 1 go ram a card as http://www.materiel.net/ctl/Cartes_graphiques/35243-Radeon_HD_3850_512_Mo_AGP.html will be useless, because the processor will curb your GC, too expensive, never forget that for 400 € you can get a brand new PC with a recent mb (pci express) and a good power supply... http://www.materiel.net/ctl/PC_de_bureau/30620-Absolute.html ...

To me the only difference between ati or nvidia are the drivers support, faster to get in nvidia more longer in ati new product's... But for agp, no matter with dirvers...