EastCoastNAZ saidI'm in the decision phase between the 15" and 17" MBP. 13" is just too small for me, even for portability. I was at the Apple store and didn't notice a huge difference between the 15 and 17. My sister has the 15 and it seems to be sufficient. Plus I have a 20-inch monitor that I just need to be able to connect. But then there's the irrational part of my brain that insists I need the 17"..ugh!
Good luck with your decision.
Not sure what monitor you have, but we kept a relatively new HP flat screen when my partner's PC died. There's a small Apple converter device we needed to buy to go from the Pro's small video-output socket to the larger HP plug, so be prepared to do the same.
Otherwise it works well for him, as it's a bit bigger than the 15" notebook screen, which is set to remain dark when the HP monitor is in use. In fact, with the wireless keyboard and mouse he has, the Pro at home is basically used like a Mac Mini box, the computer tucked away and hardly ever touched. Only when it goes "on the road" are its own KB, touchpad and screen ever used, somewhat like the DuoDock concept Apple tried some years ago.