you have for the Nvidia card the proprietary Drivers that can be installed during or after the Live CD installation. So its not a problem to install them. One click away. You also have the open source version of it, the Nouveau version. It is good, but if you do pick Nvidia I highly recommend (Until Nouveau catches up to the proprietary one), to install the proprietary version of the Nvidia driver.
Now for the Intel, it is my understanding that it will work out of the box but to fully have the Intel power of the HD series of cards you can wait for Ubuntu 11.10 or upgrade 11.04 when it comes out. There has been several updates regarding the Intel HD series.
But if you tell me, which one runs better, faster with little to no hassle, then I would go with the Nvidia using the proprietary drivers.