I've had an internal Hauppage win pc card since 1996 and it has performed flawlessly through win 95, win 98 and now win xp upgrades. My friend has bought a newer version that comes with IR remote - works well.
The picture quality in a strong signal area is superb, and I use Virtual dub to record tv to Divx on the hard disk.
External use more desk space and only have advantage of not needing to open up the case, but they are very easy to fit and work with just about any modern graphics card. I've ran mine on Matrox Mystique, Voodoo 2 Voodoo3 Geforce MX and now Geforce 4 Ti 4600