SoftQuadro enables the disabled DCC features in the GF3. It is free, easy to do, and easy to remedy if you have problems so I would suggest trying it and seeing how it works for you. It should offer improved performance.
In my experience there isn't much difference between brands when dealing with nVidia based cards.
Whether the GF3 Ti200 @ about $160 is better than a GF2 Ti for around $90 is the bigger question. Both can be hacked to Quadro2/DCC specs but it still isn't really clear which is better for 3D modeling. The GF3 is better for playing games but the GF2 seems to work better in a lower spec-ed PC.
What Apps are you going to use, and what platform will you be putting this all in (AMD, Intel; Win2K, XP, etc.)?