Best place at Monza?

May be...

I agree with the pit straight. Try to get a place near the end of it. That's usually the best place to see overtaking. Near the end of the back straight is a good place too.

Is it better getting a seat on the pit straight or one of the corners?

I know Monzas the fastest circuit but I don't know whether to get a seat at one of the corners so I can actually recognise the cars.

Go for the pit straight. The cars may pass by at full speed but you get to see them come in and out of the pits at the speed limit, you get to see the pit crew in action and you get to see the start of the race.