Never bought a PMS5003, couldn't find any real data suggesting it was better. The only indication I had was the PMSA003 was newer, so I ran with it.
I've had one running 24/7 for 9 months now with no issues. I checked the accuracy outdoors relative to PurpleAir sensors in the area and they were with a percent or two which was pretty close for such a simple experiment.
How was your experience with the PMSA003? We used it before but believe that the PMS5003 has more stable readings and a longer life time.