For what do you want to use the MBP for? Will you computational needs profit from the extra screen real estate?
PS: I have the 17" MBP and also had a 2008 15" MBP with 1440 x 900 pixel and have a 20" iMac with 1680 x 1050 pixel. For my needs (video and photo manipulation), 1440 x 900 is not big enough. 1680 x 1050 is okay, but not comfortable. 1920 x 1200 is really good, but sometimes even that is too small.