I could have sworn there was a thread that discussed this but couldn't locate it, maybe I wasn't hitting it with the right keywords.
What's the main concern for 1 vs multiple projects? I can think of a few to start:
more work on the developer to keep things organized and reduce unnecessary repetition
more overhead
more loading screens as the end user jumps between projects.
The only potential issue I saw with one big project was with a certain large and poorly designed Vision project (dozens and dozens of nearly-identical windows) and the poor designer would always freeze up for a few seconds just opening up the Project Tree.