My preference is desktop DEFINITELY!! (she said posting from her nook tablet, rofl)
We have a couple tablets, a netbook, couple laptops, and a couple desktops (big busy family) and my preference always leans towards the desktop. The speed is the deciding factor for me.....nothing in this house comes close to the speed of my quad core HP.
Plus, laptop touch pads always annoy me, lol
As for operating system, my desktop has vista. The other dekstop here has windows 7.....I think kevin has 8 on his laptop. They are all ok to me...no real preference. I thought I hated vista when it first came out....turns out vista was fine, I just hated the slow a** dell it came with! LoL