Well Ive only had a 13" so far. The 17" is tad to big for my taste. and Id be getting an SSD instead of just a 7200 drive. The 15" might be slightly faster because of the drive and a higher resolution compared to screen size since it has the upgraded resolution, not sure.
My pick will be the standard 15" and then buy ram and an SSD on my own

But your 15" there isnt the standard, its the expensive standard with a better drive it looks like. Id probably choose the 17" and then buy ram and an SSD separate between those too, feels like I could get more for my money that way.
Hard for me to say what is your best option. I wouldnt want to pay for a 7200 drive though, thats money wasted since Im planning for an SSD.