You will not really notice a difference in practice, perhaps if racing. 10 speed is better if teamates are riding shimano, 11 speed if their on campag.

[digression]That said, if someone had of given Cadel a shimano 10 in the vuelta, I'm sure he could have limped across the line and retained 2nd maybe.[/digression]

I went from Tiagra 9 to 105 10, and regarding noticing more gears, well, no. In fact, I use less gears. I had a 25-13 on the Tiagra, and found the 13 was inadequate, and have a 27-12 on the 105. I used most of that stack for the Tiagra, but only about 5 cogs on the 105.