The 628 underwent a revision a few months ago that replaced the radio, so the performance data here may not reflect what you buy today. However, both devices use Atheros radios and feature 2 dBi antennas. I would expect range to be similar with the performance advantage going to the 655 as it is a 3T3R design. Performance also lies in your choice of client, so you may not be able to take advantage of a potential performance difference anyway.
Both use Ubicom CPUs, so QoS should be identical.
You are describing the ability of your phone to handle interference. This is a separate function from its ability to cause interference. If your phone allows you to manually set a channel, then you can work around the issue.
Since range is the first thing your reply brought, it's probably important to you. Although moving to the 5 GHz band allows you to escape from interference in the 2.4 GHz spectrum, the use of a higher frequency results in reduced range. You exchange one problem for another.