One 20Mbps WAN vs two 10Mbps WANs

[zinder]

pfSense ver = 2.3.2

I currently have 1 DSL line of 10Mbps down and 1Mbps up. I have the option of adding a second 10/1Mbps DSL line from the same ISP or increasing the speed of the current DSL line to 20/2Mbps. Is one better than the other? I know it is a good idea to have 2 WANs from different ISPs for failover (not an option), but is there any performance advantage to two 10 WANs vs one 20? I already have the extra NIC I can use.

Thanks,
David

[jahonix]

Two WANs to the same ISP are a problem on its own. Usually you get the same gateway from you ISP for both connections which makes it hard for your router to route different way.
And two WANs will NOT sum up to double speed, e.g. you will not be able to download a singe file with 20MBit/s. With load-balancing you can get 2x 10MBit for pulling different data.
A single 20MBit/s line can use the whole pipe with a single download or such.