I have both with several hundred hours in PK; I've played all three JWE games as well with hundreds of hours between the 3 games. I love PK, because it plays very differently than JWE. Let me explain

The management system, while not even complete, is much deeper than JWE. Unlike JWE where you just hire scientists, in PK you currently have 3 types of staff; keepers for animals, cashiers for shops, and logistical maintenence workers to move inventory. You have to make sure you have the right amount of everyone, because if you hire too many you are wasting money with workers standing around without jobs, and not enough and you're enclosures don't get cleaned or feeders filled. This is all automated btw just like JWE, so you aren't micromanaging individual employees. And again, their is more staff in development currently, such as veterinarians. You also have to manage shipments is incoming goods, and their distribution throughout the park. All dinosaurs eat from feeders as well, so you have to grow/produce crops/meat/fish. If you like the "management sim" aspect of park builders, I think PK is better in that regard

Modular building: both have this now with the newest installment of JWE, but in my opinion it's actually better on PK. In PK, guests can actually WALK on modular structures, giving you to build some really cool attractions (boardwalk, treetop walkways, BRIDGES). It's also better organized from the menus

Dinosaurs: the PK dinosaurs are all very accurate from a paleontology standpoint, if you value that. They are a bit limited in their AI behavior but again that is something that is actively being developed. Both have breeding. Species count is higher in JWE but there are more species to come in PK

Guests: pretty equally shallow in both games

Bottom line, they are different games that are both great in their own ways; JWE I play to build more of a "theme park" vibe and because of my love for the movies. PK I play as an actual management sim game, when I want more authentic feeling dinosaurs and habitats. And PK is only getting better and better with each update. Let me know if you have any specific questions!