On long flight (8 hrs+) both the availability of 2 aisles (and thus the chance to walk around) plus the less tube like construction of the cabin militates for the wide body.
Recently flew LHR-GIG and back on a BA 777 and got to thinking just how constrained the pax would have been on the 707s, DC8s and Comets of days gone by - somehow the trip seemed longer than trips I've made to Singapore or the US West Coast.