Copied this from Reddit-- does a great job of listing all the reasons I like it better
....... can't figure out how to use spoiler tags
Weapons - 3 different shotguns, 3 different sniper rifles, 2 smgs, 4 assault rifles, 3 pistols. PUBG wins out here.
Attachments. Clear PUBG win.
Helmets - 3 types in PUBG. effectively 1 type in H1Z1 as they have the same characteristics. 3 levels in PUBG. PUBG win.
Backpacks - 3 types in both if you count the satchel in H1Z1. Even if I'm being generous.
Armour - 3 levels in PUBG. 2 types in H1Z1 one of which is quite uncommon and the other has to be crafted and the materials aren't always available. PUBG win.
Transport - H1Z1 has 3 cars and you can launch yourself out without concern. PUBG has 3 cars but you will damage yourself if you jump out at speed. This one is a preference thing. H1Z1 is more arcade so this style suits it to a degree, So I call even BUT this is the transport entry - PUBG has boats. PUBG wins.
Graphics - even on very low settings PUBG looks better then H1Z1. Camouflage works and bushes are valid concealment unlike H1Z1 where you will be seen in any bush as a black figure. PUBG wins.
Map - both have their good points. H1Z1 is too open which makes cars which are already devastating too dominant. PUBG has very definite chokepoints but these are overcome by use of boats and swimming (yes PUBG has swimming. Big difference - PUBG has a second map on the way. H1Z1 still has many issues to fix on their only map. PUBG win.
Weather - PUBG has weather H1Z1 doesn't. PUBG wins.
Gunplay - no reason except maybe shotguns to go FP in h1z1. Hipfire is very accurate and 3P is the only mode you need. PUBG has much nicer gunplay IMHO. This is also a preference thing. I'll call it even only due to that otherwise it's all PUBG.
Modding - PUBG will come with mod tools. PUBG win.
Servers - PUBG will allow server renting H1Z1 have rejecetd this idea many times including for Just Survive.
Skins - if you like pink H1Z1 is the game for you. H1Z1 win I guess...
Community - H1Z1 is so full of toxic players. I've had great interactions so far in PUBG. PUBG win.
Playstyle - if you want a quick, no thought carmageddon game H1Z1 is for you. if you like positional play, (wo)man vs (wo)man and tactical thought - PUBG is the way to go. Even - up to the player or even your mood.
Game stability and support - even in Beta PUBG is the clear winner here. Support from Daybreak is pitiful. H1Z1 servers are a mess and fall over regularly. PUBG wins.
Spectate for team - PUBG has it - H1Z1 promised it for the past 2 years.
Resuscitate for team mates - PUBG has it H1Z1 doesn't.
Bleeding - H1Z1 has it PUBG doesn't. (Except in team modes)
Different shoe effects - shoes in PUBG are strictly cosmetic at the moment. H1Z1 shoes have various effects including speed and different stealth levels.
Summary - I used to love playing H1Z1 KOTK on the original map bugs and all. The new map brought a whole new series of issues and a new playstyle. Since playing PUBG over the last 3 weekends I haven't played ANY other PC game. I couldn't face another game of Car1z1 that's for sure.
IMHO PUBG is a much better game BUT if you like arcade 3rd person precision shooting and jumping out of cars KOTK will be your game of choice in BR genre.