Would things be the same if Anakin went with Obi-Wan?

[bWhat if Obi-Wan has been the 1 with his saber at Sidious' neck, would he have cut off Obi-Wan's hand/arm?][/b]

No. Sidious would have killed him much sooner than this. Obi Wan was the only
real threat to Sidious plans (not to Sidious himself, mind you).
Go figure. Obi Wan is the catalyst for Sidious' undoing.

 

Palpatine would wait for Anakin to come home and then resume his manipulations, while using other events to keep the Jedi occupied. Grievous would be dead, but Sidious can easily assume the leadership of the Confederacy. Thus he can delay the war long enough to get it done.

 

think about this.

-grievous is dead, and mace, agen, kit, and tinn all go to confront the chancellor.
-this is perfect timing, as the jedi are here, and the temple is pretty much defenseless.
-palpatine kills the jedi, initiating order 66.