13" MacBook pro + 17 inch hp display or 15" MacBook Pro?

So, I'm getting a MacBook pro to replace an old hp desktop. I was wondering if it's better to get a 13 inch and keep my nice display for home use or get a 15 inch. The first option seems better because I have a nice sized display at home and I would have the portability on the road. Even though, a 15 inch MacBook pro has better graphics performance for games and stuff. Also, it requires less work than hooking up my computer all the time. I would like to know what's a better option. Thanks