1) I don't have to open or unlatch anything to use my phone. With my previous phone wallet, I had to open up the case itself, which made my phone difficult to use with one hand while on the subway. (Also, one time as I was opening it, my phone flew out of my hands and fell down four flights of stairs but whatever.)
2) My cards are hidden from view, and because of the magnetic clasp they feel secure. I honestly can't imagine a way for them to slip out.
3) As far as phone wallets go, this one is pretty slender! It doesn't fit in my pants pockets (though I typically wear pants designed for women, so what does?), BUT it fits in my jacket pocket and is easy to hold with one hand. So yes, optimal for selfies.
4) It's sturdy and protective. I drop my phone multiple times a week and somehow (I'm assuming in part thanks to this case?) it still functions.