The price tag is deceptive. AIOs getcha in cost over time.
With an air cooler, you deal with fan replacements.
With an AIO, it's the fans, and the entire unit. Once the pump goes, or shows signs of failure, there's no salvaging it since the vast majority of AIOs aren't serviceable.
You throw the whole thing out, save for the working fans, and buy another cooler. Or, if you're rough enough with it to cause a leak, that can get pretty expensive too.
Returning to topic: you should figure out the new chassis if you're about to get a new one, then decide on the AIO. For example, the Liquid Freezer II has a thicker radiator that normal(38mm Vs 27-30mm), and runs into clearance issues in some chassis.
You are not missing much by way of good AIOs. Most of them are made between 2 companies(Asetek and Coolit, and even fewer are in-house designs.
As long as you pick a modern unit, you're pretty much golden... but avoid Msi Coreliquid R/RH/C/P. Those are some of the most unreliable AIOs I've heard of lately. Kraken M22 is down there too, but you're not looking for a 120mm AIO.