I use a straight spotting scope, although like most people I find the angled more comfortable. I use a spotting scope, 15X bino and LRF interchangeably on my tripod, and have each one mounted on a separate quick release shoe. I spend most of my time spotting with the bino, and switch back and forth to an LRF. For really long range work, I use a spotting scope and LRF. It's a whole lot quicker to switch back and forth between spotting glass (either scope or bino) and the the LRF if I don't have to readjust the tripod. So, I use a straight spotting scope.
Shooting service rifle competition or birding, I use an angled scope.