THG many years ago did a test on onboard and PCI NICs. It would found that the Onboard NIC used extra resources which lowered the performance of the PC by a very minor amount. That was at least 6-7 years ago, if not a little longer. I believe it was at the onset of NICs being integrated.
Anyhow, what you're looking at with the gaming NIC is a more expensive and better chipset. The short answer: The gaming NIC is better. The truth though is that unless you have a top of the line Internet Connection, the NIC isn't going to matter that much.
Your bottleneck is your internet connection. If you're running 8MB Cable with a 2MB upload a gaming NIC might give you a small performance increase. If you're running 2-5MB Cable, probably not worth your time.
PCIe is the newer version of PCI essentially. If you have extra PCIe slots, use that. It'll allow faster communication along the bus I believe. I'm a bit outdated on computer hardware but PCIe is the newer, better version.
Overall, look at what you spend on gaming. If you have top of the line everything, might as well go top of the line on the NIC. I game a little and I use an onboard NIC. I don't know that I'd waste my money on a gaming NIC. I'd put the money into something more useful, maybe upgrading a video card or paying for a few months of a faster Internet connection upload speed.
yeah I have a 20mb/6mb Comcast setup with a D-Link dgl-4500 and cat6 550Mhz cables to keep my ping as low as i can, and the main thing i wanted to know is, would an Intel or Rosewill adapter behave any differently than my existing onboard NIC?
like this $30 one http://www.newegg.com/Product/Product.aspx?Item=N82E168...
would there be any difference? ..cause a gaming network adapter seems like the biggest ripoff since ripped/patched/dyed jeans.. =/
$30 NIC on on a good server, you'll have a 50 ping.
$100 NIC on a good server, you'll have a 45 ping.
There are so many other factors involved that the gaming NIC really isn't going to help that much. All the equipment your signal is being routed through, etc.
Your NIC supports 10/100 at least. Your connection at best (and unrealistic) is 20 down, 6 up, well within the supported feature of your NIC. Now, your Router should have a 10/100 WAN port. Many other WAN ports on routers were only 10/mb. That might be something you'd want to check into and definately invest in if your current router is not at least a 10/100mb.