Is there a big (i.e. noticeable) difference between the grappling ability of brown belts and black belts? If you were to see two BJJ practitioners grappling, but you did not know what belt level they were at, do you think that you'd easily be able to determine, after a few minutes, who is the black belt and who is the brown belt?
I don't think so, but then again I a newbie at this.
When answering, could you guys also comment on whether or not determining who is the black belt and who is the brown belt would be any more, or any less, difficult if they are wearing a gi or not? Assume that both guys have not trained in any other grappling art other than BJJ.