Probably not much, but I would expect the rhetoric to appear less rehearsed and stereotyped ...
You think, perhaps, that in the event of a
real terrorist attack Bush would have a better speechwriter?
No, that's probably not what you're thinking.
What
are you thinking?
Can you give us, perhaps, a sample paragraph of the sort of rhetoric that we should have heard in the event of a
real terrorist attack?
... and for declarations of war/more war to wait until there was conclusive evidence identifying the perpetrators.
Well, let's look at the two speeches you cited.
Bush says:
The search is underway for those who are behind these evil acts. I've directed the full resources of our intelligence and law enforcement communities to find those responsible and to bring them to justice.
Now, obviously he can pledge to search for "those responsible" without knowing who they are, and we should surely expect him to do so in the event of a
real terrorist attack, wouldn't we?
Note that the speech does not lay blame on anyone except "terrorists", which the perpetrators were simply by definition.
In Blair's case, he
did know who the perpetrators were, hence his reference to West Yorkshire. It is not in the least surprising that he should blame Muslim terrorists when the police had established that the culprits were, in fact, Muslim terrorists. What else would you expect him to do?
In neither speech is war declared.