Back in the day when I was starting my first real time application, I did run some tests between user events vs queues. The trace execution toolkit was my close friend back in the day. I was worried that user events were a shared resource but it turns out they are fine to use in a RT application especially for triggering. However, there was one major drawback to user events, priority. If I remember correctly, you can not interrupt an event structure with another event structure (i.e. two different event structures). So, a higher priority event could not run until the lower priority event structure was finished. I ended up using single element RT queues and timed structures. But I still use user events quite a bit for sending triggers with data to other low priority threads. User events are very good performance wise in RT applications.
David