h1z1 is very basic in its loop - you land, loot a backpack, helmet, gun or two, and some first aid kits and maybe body armor if you are lucky. thats it, no one ever does any of their stupid ass crafting shit and it feels like you spend the rest of the fight humping it towards the circle, god forbid any vehicles ever spawn near you. after the first few pickups you are mostly just looting ammo, whereas in pubg you are almost always looking to loot and it brings up some real crisis moments where you WANT to loot someone you just killed but doing so will probably get you killed.
its really just the really small, small things that make pubg better. first, a much wider variety of weapons PLUS the fact that most weapons have 3 or 4 attachment slots means there is WAY more variety in weapons and their configs, and you spend a lot more time hunting for that perfect 8x scope or kar98 sniper rifle, and you have to make some quick strategic decisions on whether you are going for a camper room game with shotgun or a m16 mid range game with a 4x based on what you loot early on.
games also start way quicker in pubg since default maps are 100 size, whereas h1 is 200 and waits a lot longer to spawn a new game. Its 1 minute or less almost always for pubg to start a game, it can be 3-5 mins for h1 which is a huge difference.
finally the start spawn is much nicer on pubg, you fly across the entire map (random vector) on a plane and jump out when you choose, whereas with h1 everyone kinda just starts at a random parachute point so people tend to clump up more. With pubg you can choose to go to the few heavy populated initial zones and claw your way out with minimal gear, or you can find a secluded spot and play for final 25 with few encounters. Also the energy drink stuff is nice in pubg, not just medkits to recover health but drinks/painkillers to have a regen effect.
and yeah beyond the meta game the pubg devs seem pretty focused on making their game really good and just work on 1 thing at a time per month, with a high laser focus on performance and stability. Daybreak seems kinda run by clowns in comparison, like patches that cause the game to crash when you fire a gun...