Which one should I use? I'm only using Windows 8.x, so I don't care about the fact that WM_POINTER is not backwards compatible with Windows 7 etc. I also don't care about gestures; only about raw touches. WM_POINTER's only clear advantage seems to be that it unifies touch and mouse input (but that's easy to work around with WM_TOUCH because mouse events can be checked with GetMessageExtraInfo()). Ease of use is also not an issue; I've been using WM_TOUCH already and I'm just wondering if I should switch to WM_POINTER. My overriding concern is latency and efficiency (game-related application). I can't tell whether WM_POINTER is a wrapper over WM_TOUCH that has extra overhead. Any comments?
WM_TOUCH is obsolete. Use WM_POINTER exclusively. (WM_TOUCH is actually a wrapper over WM_POINTER.)
GetMessageExtraInfo is also notoriously fragile. You have to call it immediately after calling GetMessage, or else you run the risk of intermediate function calls making a COM call or doing something else that results in calling GetMessage.