I think the biggest consideration is whether you're planning on adding another 19 down the road. If you're only planning on one 19 and don't have a black Chanel bag then you may want to reconsider. If you're planning on purchasing another 19, I'd recommend keeping the iridescent bag. Think the standard black with gold CC is either Rev or available every season, and there are often variations on black, such as the 22P grommets or 22C reverse hardware. Chanel has recently starting repeating colors but in general if I fall in love with a seasonal color I will prioritize that purchase over REV or a bag that is easier to get.
The other important factor is how the purple will work with your wardrobe. When I'm on the fence on a seasonal color, I try to think through what I'll wear that bag with, and what bag I would use if I didn't buy this bag. that often helps me when I have instant love with a Chanel bag.
I actually bought this same purple iridescent yesterday when I saw in the boutique!!! I had a difficult time gauging the color and was planning on passing until I saw the bag in person - as I was concerned it would be too close my metallic silver 19, but was pleasantly surprised that the purple read more in-person! It's truly a gorgeous color of purple and looks like it'll be easy to incorporate! I'm a huge fan of 19s, they make great everyday bags and have significant versality!!! Good luck with your decision.