The biggest difference is the physical form factor. If you look at the top pic here »2wire.com/?p=106 the 2701 is similar looking to the last on the right model (2070), but closer in size to the next to last (2700). The larger yet model is I think a 3700/3800, and then the biggest is of course the "iNID."
one diff also between the 2700 and 2701 aside from the size is the way you would assign sticky/static ips. here are the ff steps for the 2701:
Steps to configure Sticky IP for 2WIRE 2701HG:
1. Access the Home Portal User Interface(UI) by opening up a Web browser and typing 192.168.1.254.
2. Select Run System Setup Wizard on the Right Side of the page.
3. Verify the following PPPoE Key Code is populated and click Next. ( 522P-22P4-6262-22AT-F2NV)
4. Select the appropriate time zone and click Next.
5. Enter the Username and Password associated with the sticky IPs and click Next.
6. The Setup Complete page will appear when the configuration is done and connection to the internet is made. Click Finish to return to the home page.
7. From the home page select Home Network and then the Advanced Setting option.
8. From the Public Proxied Subnet(NAT/Routed) section located at the bottom of the Setting Option screen perform the following: Place a check mark in the Enable box Enter the true LAN Subnet IP in the Subnet Mask box Click Save
9. Click on the Edit Address Allocation button on the right side. Note: Make sure the Member has the device or computer set to DHCP -Obtain IP Address automatically.
10. Search for the computer name under Device anduncheck the Firewall Protection box. Note: This option allows the Members static IP address to be pingable and all ports are open for that static IP address.
11. From the Address Assignment drop down select the Public (select WAN IP Mapping) option.
12. From the WANIP Mapping dropdown select the IP address the Member wants to use on their computer/device and click Save.
13. Access the MS-DOS (Start > Run > CMD or Command) and release and Renew the IP address on the Members computer.