AIO is indeed an easy option to drop the temps on your GPU and get some performance out of it. Easy. But when you look at the value proposition, it gets a bit difficult to justify the cost. The AIO you mentioned here is costing 30k including shipping. Adding customs, it sums up to 42k. Now you are looking at a product worth 42k that becomes useless when 1. you upgrade your GPU. 2. If the pump on the AIO dies after its warranty expires which does have a fair chance of happening. The next question that arises is that is it worth spending 40k for lower temps and peace of mind.
Going the custom loop does have its own risks. but does come with benefits of its own. most of the parts are future compatible, in fact, all other GPU block. good CPU block manufacturers do provide mounting brackets for newer platforms. It's only the GPU block that is useless after an upgrade.
On the other hand, a full Custom Loop can be done is the same budget with both CPU and GPU cooling
Pros:
1. High future compatibility of the majority of the parts.
2. Pump replacement is easily available, every part is easily replaced.
3. Flexibility and Expandability (though the above-mentioned aio is expandible, there is a limit to what its small pump can handle)
4. Quieter, a single D5 at 30-40% PWM will be way quieter than an aio pump and can move more volume of water
5. Aesthetically better
Cons;
1. Risk of leaks, there are n leak points in a custom loop, can be the fittings, blocks, or the pump itself
2. Because the above needs to be avoided, regular maintenance is needed, you will have to take apart everything every few months depending on the fluid type used and do a clean. Do regular checks. It's the lazy people who end up with disasters, their blocks would gunk up causing pressure to build and cause a leak.
3. Spend time planning and sourcing and building ( some guys enjoy it so its subjective)
4. Requires discipline and patience while building. Cutting a tube short, ignoring an improper mount or fitting become the failure points.
The quality of products has improved by miles in the past few yrs gone are days of barb fittings and flimsy soft tubes. have a look at this
Video , check out Ek's ZMT(Zero Maintenance Tube) which is non-porous making your loop practically sealed, It is so stiff that I literally have to use vaseline to get the collar of the compression fitting fully on it, impossible to come undone
These were my thoughts, hope it helps you decide