I prefer Liverpool to play a fluid 4-1-4-1 formation.
Somewhat like how they played against Chelsea in the semis.
Let me elaborate a little on why I think this way.
The reasons to play a back 4 is obvious and solid enough. Nothing much to say there.
Having a energetic defensive midfielder who can break up plays from the opposition and shield the back four is ideal defensively. As Benitez had said before, if you have players like Sissoko and Hamann in that position, they make the challenges and even if they don't get the ball, the defenders can mop up the loose balls. Shields the defence very well. I think Sissoko plays that role very well. How many interceptions did he make on Saturday? His weakness of course is after he gets the ball, he is not good at distributing it. In fact he passed the ball right back to the opponents on many occasions. Hamann is a better distributor of the ball. But of course Hamann is not as young and energetic as Sissoko. But that's my case for playing the holding midfielder.
Gerrard and Alonso control the centre of the midfield in the 4 man midfield. Gerrard is given the licence to roam foward and run in to bang shots at goal. Somewhat like a "support striker" to Crouch up front. But then any of the 3 midfielders (except maybe Alonso who would play a bit deeper) can be that "support striker".
Kewell picks himself on the left side of midfield. He can run at the right backs and put crosses in for Crouch and Gerrard. Or he can cut into the centre himself and make shots himself.
On the right is where we have a bit of a problem. I still see Garcia as a striker more than a midfielder or even winger. But imagine a strong right midfielder somewhat like Kewell on the right doing exactly what Kewell does on the left and you have a very strong balance.
If you look at it, it's like dividing the team into 2. The defence which is the back 4 and the holding midfielder who form a darn solid wall, and a fluid 5 players in the form of a playmaker (Alonso), and a target man striker (Crouch) and 3 other runners around the penalty area and flanks.....
I think if Liverpool can get a solid right midfielder who can run at backs and cross and can shoot, it would make this formation very formidable. I think Benitez used this formation to great success at Valencia.
Perhaps a key to the success of such a formation attacking wise would depend on the intelligence and movement of the attacking players, ie Crouch, Kewell, Gerrard and ?Gonzales plus the playmaking ability of Alonso.
I'm still not quite sure if Alonso is really the playmaker for such a system.
Imagine Kewell overlapping with Gonzales frequently, Gerrard roaming all over the pitch up front but yet the shape of the team defensively is still solid.....the prospect is frightening for other teams!
Forget about the strikers. Let's get a solid solid right midfielder in addition to Gonzales!