It should definitely be shorter. Hit us with the basics at the beginning of the game then provide optional advanced tutorials later on. Maybe something like the training rooms you see in the Final Fantasy games.
I would argue for a longer tutorial so that the devs can explain the complex mechanics to new players.
I think that the devs might hold back on complexity if they think that it might scare off new players. But a long tutorial would compensate for this.
Although your idea has sparked another one of mine. Maybe the tutorial could be split into sections. The first section explains all the new additions so vets of the TES games can be taught anything new in Skyrim. Then at the end of that section a message pops up saying "If you are new to the Elder Scrolls games continue on, if you are familliar with the Elder Scroll games you can leave here".
After the whole tutorial another message pops up offering to continue popping up messages each time the player encounters something new. Allowing absolutely everything in the game to be explained to the new player.
The whole thing should be skip-able, but it would give those of us here who don’t want a long tutorial the option to take a quick one. It would give the devs a chance to give new players a long deep tutorial, and those of us who are coming back a second time a chance to skip it entirely.