i remember, 5 or 6 years ago i use and love TT Retrospective 5. I think it's very discreet to use in the street. Back then, i also think that Billingham people's look arrogant and it represents as a "theft attractive's bag".
But.... after using Hadley Small, i understand the quality of materials, and why a lot of people really enjoy using it. The weight, the size and the compartments is perfect and usable, unlike the many pockets in Retrospective 5 that "unusable" for me (2 outside pockets and inside side pockets).