I can do a horizontal stripe on top, not on bottom (oof, the widening effect of horizontal stripes on my hips is a truly horrible thing). Vertical stripes are not always easy either -- if the item is fitted at all, it goes all curvy over the parts of me that curve (i.e., pinstripe pants *can* work if they are not tight at all, and low contrast). But I prefer vertical stripes to horizontal -- they're just not as easy to find, in my experience. My favorites are diagonal stripes if they are placed well -- they often mask my asymmetry and don't emphasize my curves too much.
I love a good side stripe when it actually fits me with some ease!