I am not the most experienced but I have researched a lot in the recent 1 year for my Flair replacement - including the two models you mentioned. I ended up with a Lelit Mara X.
You can do some additional research, but basically with or without PID, both Profitec Pro 500 and Appartamento are still single boiler HX machines. In 2021, it's quite hard to recommend a traditional HX machine regardless the PID because you still need to do flushes to surf the temperature. The PP500 is good at stabilizing the boiler temperature, but not the group head temperature which is more important.
The Appartamento does look fantastic, but it is so outdated and IMO not really worth it if this is your second machine, there are better choices out there.
I ended up going with the Lelit Mara X - which is a single boiler HX machine as well, but it has a very unique innovation where in the brew priority mode, it doesn't operate like a traditional HX. The dual PID and smart controller actually stabilizes the Group Head temp very accurately down to 1 degree C. You can read more about Mara X, but this points out the advantage over the PP500 very well:
https://www.reddit.com/r/espresso/comments/...nd_the/g4bckw9/The price is around the same as Appartamento as well.
Mara X aside, I recommend the following machines.
1. Lelit Elizabeth (Dual boiler at around RM7000. Throws PP 500 and Appartmento in the dust. I didnt't get it because my counter space is too small and I prefer the E61 look of Mara X more)
2. Breville Dual Boiler (The very underrated one, it can do pressure profiling and all for a very good price. Again, space is an issue for me, and I don't like breville's aesthetics and parts longevity)
3. Crem One 2B Dual
DaveC from the UK have very detailed reviews for Mara X, Elizabeth and Crem One at his website:
https://coffeeequipmentreviews.wordpress.com (but his Crem One is the top of the line version).
Does the mara X have pid? because from what i read, doesn't specifically says it has PID.. only that it has a few priority setting to pick from.