Regular Ol' three ring binder
Pros:Cheap. Custom cover. Adjustable page count.
Cons:Feels cheap.Can get scuffed up.
Anecdote:In college I had some support materials in a drawing presentation that where in a binder where a plastic sleeve was scuffed and something had mysteriously discolored a spot on the back. The guest reviewer (nobody famous) gave me a C based on this alone. Meanwhile a girl who tied yarn onto a nail in the wall got an A for her drawing project. Love it.
Pros: Number of pages can be adjusted. Relatively portable. Artwork feels very safe. Flap for business cards. Matches your couch?
Cons: Way too expensive. You'll never use the zipper and handles seem entirely unnecessary unless you've printed your work on lead plates. Once again, the plastic sleeves create a glare in a convention environment. Binder part has a million loops so it would be a huge pain to make your own custom pages. Portfolio will want to close on you.
Anecdote: I fondly remember showing my work for the first time at Gencon and being nervous and bumbling around with that zipper. I was screaming in my head, "oh god why! Why did I zip it closed!? Must unzip before client runs away!"
Pros:Very portable. Lots of sizes. Can insert custom front. Easy to make custom pages where there won't be shiny sleaves creating glare. This bad boy is so thin that you're forced to limit the size of your portfolio which is probably a good thing.
Cons: It's able to be so compact because of the unique binder rings. This uniqueness means that viewers often fumble with how to turn pages. Turning pages means slide then flip with this case. Viewers don't seem to mind but there's very little clearance between rings and spine so you're dealing with potential for accidental wear and tear on a very thin piece of paper. So you need to either get those little plastic rings to put on your paper and strengthen the paper or use heavier stock paper.
Also, you'll have to spend a couple of minutes after ever review resetting the pages as most viewers won't know how to move the pages back and even if they do, you pretty much have to move one page at a time.
Anecdote:I remember showing my work at Gencon and being nervous while art directors bumbled with turning the pages. I was screaming in my head, "oh god why! Why won't the pages just flip normally!? Don't give up AD! Keep trying! You'll get it! There's good artwork on the next page!"
Pros: You can put 11x17s in this bad boy. Artwork feels very safe. Nice for when multiple people are looking at your work at once.
Cons: It's pretty darn big. You feel like a jerk carrying around this thing on a convention floor. You'll feel tempted to carry it above your head and expose everyone to your armpits. You also can't customize the cover really. It may be a problem with AD's at smaller booths because they won't have a table to sit down at and look over the work. So they have to hold this monstrosity in their hands.