Friends and roommates saying I should go with NZXT Kraken X72 / Z73. Some others saying Corsair H150i Pro is better. I'm aiming to OC a I7 9700k to 5ghz. I was going to use NH-D15 or NH-U12A but I heard they only compare with 260-280mm rads. 360 Would beat even the biggest and best air coolers right?. I know open/custom loop is best but what is my best option for AIO?. Thanks.
For aesthetics, the NZXT and Asus OLED models are a great choice. For actual performance, the arctic liquid freezer II 360mm is probably the best considering that the fans that come stock with it are super close to noctua fans, in terms of noise, at similar rpm and they move a ton of air.
an Astek AIO isn't going to necessarily beat an air cooler. It might but it depends on way too many variables for anyone to tell you with the (lack of) information you gave (and even if you did give info on your setup you'd need to find someone with an identical setup who tested both an air cooler and an AIO).
if you have terrible case airflow and you mount the AIO in the front you'll probably get better temps with an AIO, if you have good airflow and/or mount the AIO up top then a high end air cooler is likely to perform as well or better.
the only difference between the majority of them is the included fans, get one that uses a Gen6 Asetek pump and otherwise buy whatever is the cheapest if you're going to swap the fans and buy whatever has the best fans if you don't plan to.
a 360 also generally doesn't out perform a 280 either. the limitations on CLC AIOs isn't radiator size, it's flow rate. throwing more radiator size at the problem doesn't do a whole lot.