Doesn't really matter which it is though unless you are doing LAN parties. Internet connections typically run 20Mb/s or less. The highest I've seen on a consumer level is Comcast's 105Mb/s download speeds (mind you
8Mb = 1MB) and that service costs $200 a month. Oh and the upload is only 10Mb/s
It matters... Everything I have connected via wired connection is gigabit ethernet. Connecting a fast ethernet device to the network slows down the entire network considerably. I don't understand why the slim model doesn't have Gibabit ethernet. It should.
Connecting a 100Mbps NIC isn't going to slow your network down. My entire network is gigabit speed, with the exception of a 100Mbps NIC in my network printer and Xbox 360. I still get transfer speeds of over 100MB/s between PCs. 100Mbps is more than enough
for any HD stream.
Unless you want to transfer the an entire HD movie file in a couple minutes 10/100 is more than enough. If you look at Blu-Ray movies they never use more than 40Mb/s+Audio during playback. As far as I know any good router or switch with a Gigabit spec has
no trouble auto negotiating a 1Gb connection parallel to a 10Mb or 100Mb transfer. Some cheaper ones might have to pull everything down to the lowest though.