I have two ADSL routers that, when coinnected to the network, provide completely different connection and attenuation rates. Any reason why that would be?

The first is my D-Link G604T which has a line attenuation of 26 Down 24 Up and has a downstream rate of 7616 kbps and an upstream of 416 kbps

The other, the one I am using at the moment, has line attenuation of 21 Down and 11 Up with a downstream rate of 7616 kbps and a much higher upstream than the other router of 640 kbps.

I'd be interested to find out why the difference

ps  Same computer, same phone jack, identical settings in modems. Both 4 port routers/modems.  Wireless is not enabled in the 604