I wonder to what extent the experience level of the participants contributes to the overall perception of "busyness" as well. I've felt a lot more stressed flying into TEB or MDW when there were a (relatively small) bunch of guys, many of whom were likely fairly newly minted, stepping on each other to announce their presence to approach than I have in other situations with substantially more participants who were content to dial the frequency, hit the ident after it was clear that there was unlikely to be a break in the action, and wait for the controller to get the job done in his own good time.