Of the 4 cases I have on my desk (I bought 3 and had 1), 2 are laptop style sleeves and 2 are folio style (hinged on a long edge).
I'm not keeping the sleeves. They only offer protection when the iPad is stored. If you want to use the iPad then you'll have to remove it, and then you'll have another thing to hold on to.
But they are also very sturdy. These 2 cases provide the most protection against impact. If I were going to carry the iPad around loose (instead of in my backpack), I would get a sleeve style case.
One sleeve has the zipper along a short edge, and the other sleeve has the zipper on 2 edges. I think the former is better because the iPad has a lesser chance of accidentally falling out. (I wish the handle were also on that edge for the same reason.) I'm a little forgetful, so there's a good chance that I might walk off with the sleeve open and the iPad at risk.
My 2 folio cases are very different. One is a basic black made from neoprene (rubberized plastic) and the other is black leather. Think of the differences as being boardroom vs basic black. Both cases have tabs to hold the iPad in place (that's why I'm keeping one).
I'm keeping the basic black case because it has zippers on 3 sides. The leather folio does not; it also lacks protection on the edges as well as a secure latch.
The case I'm keeping is the cheapest looking one of the bunch but it does what I need. It provides enough protection in my backpack and doesn't get in the way when I'm using the iPad. I can flip it shut in a fraction of a second as well as fold the cover back all the way without breaking the spine.
P.S. Here are the cases sitting on my desk right now. Most are down to only $10-$15 on Amazon.