My fear is the common "does it leak" concern.
No AIO/CLC is leak proof. They are leak resistant.
Whether they do or don't depends on how the user handles them. [I've read that the early gens were more prone to it. Now they're built like tanks.]
the noise factor between Air vs AIO liquid kits then by all means please help educate/assure me.
Most AIO/CLCs are potentially louder. Just look at the fan specs between them and air coolers. They typically come with stronger fans because of the impedance caused by the use of high FPI(Fins-Per-Inch) radiators, like 20FPI or so.
There are models that use lower FPI rads, but I don't know why they aren't more common; the coolers with higher FPI rads see optimal performance around higher fan curves, whereas lower FPI is designed around lower curves and higher rpm doesn't improve performance much on them, but it doesn't matter when some users don't really want to hear their fans.
Yes, I know about manually setting fan curves, but it doesn't change the fact that AIO/CLCs are potentially louder - the fans aren't the only factor involved. There's the location of the air pockets.
AIO(All-In-One) and CLC(Closed-Loop-Cooler), the latter gets generalized to an AIO, when it actually isn't. To set them apart:
AIO: It's a prefilled custom loop, but can be refilled and upgraded by the end user. Uses custom loop parts, allowing for some part replacement, or even expansion.
CLC: It's a pre-filled loop that cannot be opened up or filled by the user without them breaking it in some manner. Plug-n-play, then toss the unit(keep the working fans) when it doesn't work anymore.
There aren't as many actual AIOs in the market as before. Not necessarily(?) a bad thing [since most people want things to just work and get rid of them when they don't], but if one is an environmentalist, CLCs are the most wasteful of the 3. An AIO at least has the option of salvaging.
Both AIO/CLC lose fluid to evaporation(permeation through the tubing) over time. What this means is that subsequent Years will never beat Year 1's performance, but at least AIOs are refillable.
There are 3 inevitable causes of pump failures:
Mechanical: The pump will fail, it's just a matter of when.
Biological: Organic material in the loop restricting or blocking flow? That's this one. The prefilled coolant has biocides mixed in to prevent this, but they have an expiration date.
Chemical: Kinda goes in hand with biological, but the factor this time is galvanic corrosion(look it up) as a result of the majority of AIO/CLCs being mixed metal(aluminum radiator, copper cold plate). The prefilled coolant has inhibitors mixed in, but they too expire. This one is easily avoided if the manufacturers went all copper(expensive) or all aluminum(DON'T use liquid metal).