I had some years ago 13" MacBook as a travel computer and I had to use it occasionally with InDesign. Speed and performance were not an issue, but that screen size really bugged me. That was the main reason why I asked my employer to get me 15" MacBook Pro and it was suprisingly much better, 2" doesn´t sound much but in this case it really had a meaning.
Of course if you don´t need to travel with your computer, you can always get an external monitor. It sure costs less than 600 bucks. If you keep your page in Mac´s own monitor and put all the tools to external one, you probably can get some $100 cheap monitor from BestBuy... but make sure it´s the one you can connect to your MBP, there´s so many different craphic cards in MacBooks and MacBook Pros that you really need to figure it out before you purchase anything.
I think it depends on what type of work you want to do on it.
I work on a 27" monitor in the office, and at home I have a 15" laptop. Even at 15" I hate laying out spreads and print publication work. But for something like desiging logos or invites, that kind of thing... the smaller monitor is sufficent. I would have a very hard time doing indesign spread layouts on a 13" monitor.
I agree, but I just had another thought. Frequently, when traveling, there is a large TV in most hotel rooms and vaction properties. What about connecting an external video cable from the 13" MacBook Pro to an external monitor. Certainly not the best solution, but it'll probably work.
That dedicated graphics chip on the 15" models is well worth it alone. The extra space is great too. I'm sure the 13" will be powerful enough for most purposes, but the 15" is just great.
I got my 15" right when Apple did the refresh (two weeks after) and got it from CDW's outlet. Someone will order a built to order mac and CDW can't return the item back to Apple or list them, so they get dumped in the outlet. I ended up with a MBP 15" with the fastest everything short of an SSD and the stud graphics card for less than the cost of the lowest MBP, about $800 cheaper. Link to what they have now. Here would be an example. All of the stuff you will see there will be what a customer has returned in less than 30 days. When I got mine the product was out no more than 2 weeks.
APPLE MBP 15IN 2.4 750GB 8GB SD (BST 2623710 In Stock $2,645.99 $2,185.44
Just a suggestion. I'm in no way affiliated with CDW and other stores that are similar may have the same or better deals.