I have a 6620L and a 7730L. I actually can't tell any difference between them other than the menu system on the 7730L is better than the buttons only on the 6620L. Both perform so close to the same I can't tell any difference.
If you need Port Forwarding like I do Jetpacks will do this.
I also found out about a month ago if you need a static ip address for your Jetpacks (I do), Verizon will set up a static ip for all devices on your account for a one time charge of $500.00 including your smartphone. A bit high I suppose, but much better than having to use a VPN and monthly charges.