if you are going for an asetek based AIO/CLC make sure you go for an asetek gen 5 pump unit. these are much quieter than their gen 4. There are also other companies that make AIO's too. like it has already been said the main difference between a lot of these coolers are the fans. I have a cryorig A40 ultimate (38.5mm rad) in push pull config. the push pull config is worth 3-5C but also means you can run the fans a slower speed ( mine don't go over 850ish rpm). pretty much all the fans that come with AIO's are crap though. There are a couple of units that use copper rads like the fractal design kelvin series.
if you do use a push pull config make sure the fans are actually spinning at the same speeds. just because they are the same fan under pwn control doesn't mean they will spin the same. mine are set up under bios control. if you get a cheap one I would get some better fans.