OK. Lets do it here. There are 3 images below. One each for 13,15 and 17. Look at the AMOUNT of information displayed on each screen. That's one of the advantages of higher screen resolution. The 17" really isn't that much bigger than the 15. I've carried one around the world since 2006. Seriously, the drop in resolution does not justify the slight size decrease.
If you think the 17"is too big, then you may as well go all the way down to 13 assuming you don't need the graphics power. Unlike the 17 to 15 drop, the 15 to 13 drop really doesn't change the amount of screen real estate too much.