I don't think I've seen one at the top..
I'd say bottom because I'd rather not have the cord coming towards me, rather than away, when I'm using the phone. Also it seems more ergonomic for me to put my phone in my pocket with the top pointed down rather than up.
My Xperia 10 III has it up top. Damaged more than one cable by just jamming it in my pocket upside-down then realising the cable's getting smushed up. Note to self: Get headphones with 90 degree cable connectors