I'm trying to remember the last time I got into a full taxi. If it is close to full, I will wave them on so as to not take a space away from a local. Most times, I'm the first or second in. And I can't remember the last time one was full before I got to my stop either. Never thought twice about being the first one in before. If I'm the first in, they almost always end up pitching me additional services - either taxi, tour or "personal". But once they know it's not my first time at the rodeo we usually just end up having fun conversation.
When I mentioned before about the angry reactions from the white plates, it was when I was on the road clearly flagging down a taxi but if it's after sunset, it's hard to tell if the plate is white or red until they are right there stopping. Then when I said no, a few have gotten a little hostile. This isn't late night, usually just after dinner going back to my hotel (maybe 7 p.m. or so).