The 6210 also has dual graphics pipelines sobsically it can take its 256 MB of memory and split it between two monitors to run two seperate apps at the same time so Maya on one Deep Paint on the other or whatever. If youre only using a single monitor all 256 MB of storage will go to that one program running.
The Quadros are great cards as well and will support dual monitors but don't have as much RAM as the Wildcats, but they do support full DirectX so you can use it tp play games as well, something the Wildcat lacks in.
I think you may have a difficult time buying the 6210 by itself since it's only offered asa an OEM part, I don't know how the 6110 compares to the 6210, I know it's quite a bit cheaper and can be bought individually but it doesnt have nearly as much memory.
The Quadro 900XGL can be purchased from ELSA and some other manufacturers for a pretty reasonable price.
So I would say Check out both Nvidias and 3DLabs sites and compare the cards. They supply full spec sheets and will help you decide.
A friend of mine demoed the 6210 at the GDC in March and I wasn't to impressed with it's realtime refresh rates, especially when textures were being displayed. I also checked out Nvidias booth and they were demonstrating a plugin foir Maya that works with withe the Quadros allowing it to display real time shadows, reflections and BumpMapping. They used their Chameleon model running the animation inside of Maya and changing from refelctive to bumpy and all that. Pretty impressive.