The one with the magnetic tab is crappy, IMHO. With regard to cases, I like the latest Sony design the best: integrated into the back of the e-reader, with a magnet in the front of the reader.
The ones with the maps look nice
Maybe i'll just get one for kicks. They look as if they are the same as the first version of the GoogleProduct case (the non-magnetic one), with a different print on it.
The last one has a tab again; so that's out. Anything with a tab, clasp, or metal part (such as the Kindle original case) already starts at a disadvantage, especially if the case itself has a part that sticks out.
IF I get a slim cover with a magnetic tab, then it'll be the one posted above, the one that's like a 1:1 copy of the original. It has a metal part, but at least nothing on the case itself sticks out.