Captain Slug said:
The benefit, assuming your case already has somewhere to pass your tubing in through, is that you don't have to empty out your case to cut the holes needed to mount your radiator.
Other than that I don't see any specific advantages.
IMO, the only situation in which an external setup would make sense is if the w/c components could be located in a much cooler location than the PC itself.
My desk sits right next to a window and I've seriously considered moving at least the rad to the outside of the house and letting Nature have her way with it.
Just as a proof-of-concept test, a few weeks ago I pulled off the sidepanel and moved the case right next to the open window...
(note: the third Seagate HDD is in an external enclosure and the nVidia temp sensor seems to
start at 31C...I've never seen it go lower...)
I suspect that with such an arrangement the rad could be run passively (at least through the winter) although the percentage of antifreeze would probably have to be raised to prevent outright freezing of the loop.
Also, I'm not sure at what point condensation may become a factor but all in all, I find the concept intriguing.
The loss of easy portability is also an issue (which could be somewhat ameliorated by using suitable quick-connect/cutoff fittings), so I'm still waffling about really giving it a shot.
This said, without the compelling results that the (really!) "external" w/c loop would provide, I don't see the point.
If the only reason you want to go external is to make an easy setup then I'd just get a bigger case.