Which screen size??

This is almost asking what color would you choose.

What are you using your laptop for? If you are doing graphic / video work I personally think a 15" is minimum. If you are a Facebook warrior I could imagine the 13" would do a good job.

 

I would like to follow up this question with another question. Regarding the two different resolution sizes on the classic 15, is this a no-brainer and you should upgrade to the hi-res or can you get by without it?

 

It basically comes down to this:

If you plan on gaming, video editing, photo editing, or doing any graphic-intensive processes, then you should get the 15".

If you're the average user that does the typical web browsing, social networking, and document/word processing, then get the 13".

 

Possibly all

Many consider the 13" models to be the near perfect size. This even as Apple has always shorted them in comparison to their larger 15" siblings. For instance in having to settle for duel core versus quad, and no dedicated graphics.

Others want more screen real estate, so ignoring the 13" models to begin with. And just a happy coincidence or not that in paying the higher price they also end up with a significantly more powerful notebook. Some of them are also masochist enough to claim that lugging the 15" models around is no big deal, and anyone complaining in thinking of a smaller size should hit the gym. Nevertheless, some of these Schwarzenegger's in training do wear out in time, and decide that they do not need all the horsepower of the 15" and would prefer the smaller size and weight of a 13". Each will have their own reason, if it often comes down to just that.

As for right now, it is hard in cost and performance terms to justify the 13" retina versus the 15". Max out the 13" and one is verging into 15" price territory, but without its capabilities. With the advent of Haswell this autumn that may more even out. But for now, even with Apple's recent price reductions, you'll be paying a premium for a retina, and especially for the 13".

But it might be all you want.

 

I personally think that if the portability is one of your priorities you must go with the 13": it's way lighter and portable.

On the other hand you loose a quad core CPU chip, dedicated graphics, more screen estate, dedicated speakers.

It's not so easy to choose. You must consider what you are going to do with it. If you are not going to do professional video editing or gaming the 13" has the performance you need.