While being on the same channel as another network is not ideal is it better than being on a neighboring overlapping channel because 802.11 spec has methods for dealing with co-channel interference?
Or in other way, is it better to be in the non overlapping channels 1,6,11 (besides they will be probably shared between many other networks) or choose some channel between them containing less networks?
It is better to be in the same channel as your interfering signals (if you can't find a free channel) rather than in overlapping channels that are not the same channel - if you are in a nearby channel, there is interference, but no communication. On the same channel, the spec requires some cordination to share the channel.
Often your best actual bet is to run more wire, and place your APs at lower power nearer your end use devices. Using the 5GHz band is also very helpful as there are more non-overlapping channels in most of the world, and it does not penetrate walls so well, keeping neighboring signals out of your space (or at least greatly reducing them.)
