I use Spotlight, but Launchpad is terribly inefficient compared to stacks. You have to click on its icon to invoke it, hunt through potentially a bunch of different screens, click on a folder if you've organized your apps, and then click on your app. With stacks, I move my cursor down to the dock, click on the appropriate stack, and then click on my app. 2 clicks vs a button press, a bunch of swipes, hunting, and 2 more clicks.
Yes but, with stacks, I often have to do a lot of scrolling to find the app in my applications folder because I haven't spent the time to organise it all into folders. With launchpad, I would have every app in a folder (probably) so I would probably have only 1-3 pages. For me the number of clicks will be the same for the apps that I store in folders already, just with less scrolling:
Stacks: click the stack, scroll to the folder, click the folder, click the app.
Launchpad: click launchpad, swipe to the correct page (if necessary), click the folder, click the app.
I think it will be easier to find apps in launchpad because of the easy use of folders and the fact that it is fullscreen.