The Ram's "UConnect 8.4" does not feature Apple CarPlay, just has its own Bluetooth integration. We bought a Kenwood 2-DIN height radio for the E55 that had CarPlay built in and liked it. The positive of it is that the navigation and integration with the phone is good, so you open something on Maps and it shows/displays on the radio. With my Ram if I want to navigate I either have to enter the address in the on-board navigation or use my phone, I can't take an address I find easily on the Maps ap on my iPhone and then simply dump it into the truck's navigation.
The real negative of CarPlay is that it makes the radio essentially an external screen for your iPhone and you can't multi-task. We found this annoying last year when at the Albuquerque Balloon Fiesta. Laurie did most of the navigating and would plug a route into the phone, it would display on the radio through Apple CarPlay. Then she'd go to Google to look something up while I was driving and the map directions (including voice prompts) would disappear. We figured after a bit to use one phone for nav and the other phone for other stuff.
For any sort of retrofit application, I think there are a lot of benefits to CarPlay. But other than a few things I'd like to improve with the Ram's setup, I think it works better overall.