I started using the easel-style covers with an M-Edge one for the original nook. I find for regular use, the folding-over is more convenient than folding sideways (which is a relict from having a 2-page open book, which most readers aren't these days... not that I wouldn't love one) Plus. while you can prop up a side-folder on a table, the top-folder allows for a nicer angle, esp. on a cramped table.
The biggest advantage though is when reading in bed if you're a side-sleeper like me: you can prop it up sideways, hands-free, read until you fall asleep, and then so does the reader... Seldom had the issue of knocking it over and so far no damage as a result.