I'm doing distance learning with Bristol and must admit i find them very supportive and willing to give advice and guidance if and when needed. I would say, although i have no direct form of comparison, that DL is probably harder than Residential. I think this for severla reasons; firstly the obvious, support. You are in a classroom enviroment with others there to talk to, exchange ideas and so on, secondly you do not get distracted. i have found it very difficult to be able to get time where i can be left alone for long periods. This of course is down to individual circumstances, but if you are able to do residential then this problem is taken out of the equation.
I have two friends who fly for British Airways, both very switched on guys and they both say that they would find it alot harder doing the GS by DS just because its not in a classroom enviroment. Again people learn at different levels in differing surroundings.
Bottom line, i think if i was to do it again i would go residential. I think DL is for people who for family, work, social, economical commitments can not attend a 'full-time' course.
That's my ten cents worth, hope it's been of some use.
Rotormad