Actually, straight up is the most efficient, for launch and recovery since it minimizes excess weight, minimizes drag, maximizing you fuel use and your Delta V. It doesn't make it the easiest for recovery though. What launch and recovery method given current technological constraints do you think is more efficient? Are you referring air launched vehicles? their payload capacity is limited by that of the launch platform (read plane) they use, Pegasus being the most used in the US, has a very small payload capacity, and is not reusable. Space ship one, while cool, has not actually orbited.