Which Mac desktop configuration is faster and more powerful?

What is your intended lifetime for this system?

During that lifetime, do you expect to upgrade the OS and/or apps?

The 2011 iMac is more likely to reach a point where some OS or app upgrade no longer supports that model. That is, it's more likely to reach its upgradability limit sooner. This is simply based on when the machine itself was released.

Yout also have to factor in the physical size of the screen, and your upgradability limits. By the latter, I mean are you at an age where a few years down the road, you might need prescription lenses, or a lens change? Looking at a screen for long periods, or at certain distances, is much easier when you're younger. As you age, presbyopia takes its toll. It's generally easier to accomodate a larger screen that can be placed farther away.

 

What do you want to do?

Whats your definition of intensive Photoshop work?

 

Isn't the 2011 iMac still USB2? Is that a problem for you now or in the next few years? It might also affect your resale value.

 

Yes the 2011 iMac is USB 2. My wife has one. It's possible to add USB 3 via a thunderbolt station like the CalDigit.

 

You say you're comparing two desktop configs, but then show us a 2011 desktop vs a current model rMBP? Generally speaking a desktop gives you better performance at a lower price point, but at the same time a two year newer machine has improved technology in it, vs the older unit.

Unless you'd rather go with the laptop for portability's sake, my inclination would be towards a desktop, but not that 2011 model above, but the current version, late 2013, and unless you're in a hurry, I'd wait till late summer for rumors re an imminently updated model. It will definitely cost you less than a comparably equipped rMBP, in addition to the money saved on that external display you were considering.

Also I'm very partial towards PCIe-based Flash Storage; imho it's money well spent. The difference in speed vs an HDD varies from noticeable to dramatic, and you will appreciate that doing intensive Photoshop work.

 

The rMBP will have the edge, and be the faster machine as you're jumping two processor upgrades from Sandy Bridge on the 2011 iMac to Haswell on the 2013 rMBP, as well as the faster graphics; it is after all a two year newer computer. But unless a laptop is a must for you, I wouldn't waste my time or money to upgrade to that rMBP at this time. The biggest advantage of that would be the flash memory and USB3.

Unless you are extremely dissatisfied with the performance of that 2011 iMac, and can't wait any longer, imho the smarter thing would be to upgrade to the next version of iMac, sometime later this year, and use that money you had planned to spend on an external display, towards flash storage and upgraded graphics. At that time you would still be able to get a decent price for your 2011 iMac on the resale market.

As I mentioned before, if you do not need the portability of a laptop: desktops=better performance for less $$, as compared to same generation laptops. Good Luck!

 

Glad to help. But if you're not in a rush, you might still consider waiting for expected updates to the rMBPs, sometime in the not too distant future. A faster processor and better graphics are a given, and you might possibly get more flash storage as a base config, among who knows what else.