The other thing to note is the lack of 11 tooth rings in Shimano. The 11 tooth cog can make a 3 mph jump in the top end of bike. You could find yourself wishing for a gear that Shimano does not offer. Yes, quite a bit. Campy makes a thicker cog than Shimano.
More steel means longer life.
If you ride once a week you will probably never notice. The guys that ride 200 or more miles a week will tell you the Campy cassettes run longer. With the exception of Dura-Ace the Shimano cassettes come joined together so that it is not easy to make cog substitutions. If all the big cogs are joined into a bundle it has enough surface area to prevent this. Campy makes each cog in a precise stamping that allows each cog to be self supporting.