I prefer straight. I've owned and used both. My primary uses are @ the range on a tripod or from the pickup on a window mount. I find it much faster to both find what I'm looking for in the spotter quickly, as well as reference back to my viewing subject without the spotter using a straight body.
If you're constantly looking "up" with a spotter, say from a valley floor up onto a mountain, I can see the allure to an angled body for some folks depending on the terrain they hunt. The whole unit sits lower which should make it steadier on a tripod. Looking down into your spotter is probably more comfortable than crunching to get "under" it trying to look up.
