Good question! As a relatively long time
Broke Straight Boys member, my answer would be, while there is some overlap of members who comment on both, the two seem to have been on an overall basis two quite different groupings of
Broke Straight Boys members. At the risk of over generalizing, the scene posters are more spontaneously responding to the video just watched and also are members who never bothered to do what has to be done to sign up for the Forum, whereas the Forum posters tend more to be pressing their personal preference agendas while commenting on a scene (e.g. age and body type preferences, straight versus gay or bi preferences, etc.). Also, it seems to me that the scene posters are generally more positive and the Forum posters are far more negative (with exceptions on both scene and Forum posts of course). Frequently negative Forum posters express disbelief at how much higher a scene gets rated than they would give, and that positive vs. negative general distinction is one answer to that. I think that where Mark is coming from in encouraging us to post both on the Forum and the scene comments is to get a better overall membership sample in terms of what the overall membership and not just us Forumites think about in rating a scene. For that reason, I do try to comment on both.