I do, I can write a full song, with blast beats and rolls, in such a short time, in GP5, like you wouldn't imagine. Because the key shortcuts are intuitive, and also especially, the copy/pastes function of GP. You don't need the mouse except to navigate in the measures. Also, I know the midi notes by heart to program drums. It's almost like writing drums like I would write a text in word. Then I like to polish in reaper (velocity, humanization etc) or to divide notes between several types of cymbals since the standard midi mapping is not as rich as would be a metal drumkit for example.
A second reason why is that in any ase I need to keep tabs for my songs, and I want them to be realistic, with the full orchestration if there is one, synths, etc, so I need to tab those drums anyway. Then you just export the drums midi the day you wanna produce the song, and you're good to go.
GP6 is horrible though, what a backwards move, buggy, slow, copy paste functions unintuitive and lacking, and the worst, no midi notation for drums anymore (in tablature view)