Your question is sort of like asking "Who is right, the Democrats or the Republicans?" There are tons of opinions on the "right" way to tongue, supported with "facts" and "personal experience." Expect your head to spin if everyone chimes in!
My best results have come from not thinking about tongue position and such too much, but I've made some observations:
- Keep the tongue relaxed, as if it is "melted" in the mouth: let it "ride" on the airstream.
- Concentrate on the sound the tonguing produces, rather than the action of articulation itself.
- Remember that speed involves more than forward motion, also backwards as well.
Good luck, and have fun!