Originally Posted by lamarguy
Cam-lock - Not sanitary, easy to attach/detach, reliable seal, and inexpensive.
Tri-clover - Sanitary, not as easy to attach/detach, reliable seal, and expensive.
IMO, for cold-side fittings (e.g., fermenter), tri-clover is best. For hot-side fittings (i.e., brew rig), cam-lock is best.
I'm going to second Lamarguy here and add a few points. I have and use all three and they all have their good and bad points. I'm not voting cause there is no "all of the above" to vote on.
Tri- All my cold side stuff is tri-clamp, except my wort pump which gets heat sanitized anyways and has threads itself, so there's no getting around that. The best part of TC is that it's sexually androgynous. You don't have to worry about an Adam and Steve in there, or what not. This is a concern for me as I have in-line everything (Ox,Carbing,Filtering,blowoff,yeast harvesting, etc...). This is the only really sanitary disconnect too so I think better for fermenters and such. Also, the large internal diameter of a 1.5" tri-clamp makes for putting things inside like an in line diffusion stone (which you can do with pipe too, but that's not sanitary) or a sock screen gasket for, as in my case, second stage filtering pre plate chiller.
Cam-lock- As much as I wanted to just stick to one or two, I ended up just purchasing the cam locks for the hot side. They are way more useful for 'patch-bay' type applications where you need NPT anyways, like a plate chiller.
Quick Disconnects- I'm assuming you mean the CPC plastic ones. They are useful for things, although I am sending many of them back to McMaster.. For one, they are the only one of the three that comes in an elbow configuration (without adding a street elbow) and also a "thru-the-wall" mount configuration too, which I use for my water in. Also of note is that they can come with shut-off valve configs too (just like ball locks, basically). The bad thing is that they have a little cross thingy in the inside (really only there to push open the shut-off valves, but the non shutoffs come with them too... so you can intermingle). So if you are using them for mash recirc, they can trap grains. I'm replacing that particular one with the proflows camlocks.
D- All of the above.