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They are about the same price ($100 difference, iMac $1699, Macbook Pro $1799), and

iMac: Quad Core i5 2.7GHz
Macbook Pro: Quad Core i7 2.0GHz

How can you tell which processor is faster?

(the iMac shows 4 processors in the Activity Monitor, while the Macbook Pro shows 8 processors)

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GeekBench has the MBP about 12% faster than the iMac. primatelabs.ca/geekbench/mac-benchmarks However, take that with a grain of salt since it's close enough for your workload and peripheral I/O to swing it the other way. –  Art Taylor Oct 10 '11 at 3:35

2 Answers 2

up vote 2 down vote accepted

They are the same, or the i5 would be infinitesimally faster, which would translate into no real world difference (certainly none above perceptual thresholds).

This article compared the i5 750 (2.66 GHz clockspeed) vs. the i7 860 (2.8 GHz clockspeed). Data shows the i7 inched ahead by an average of a 3% performance improvement on the whole. Make note that this is a lopsided comparison in favour of the i7 (if only marginally). The Macs you list would favour the heavier clockspeed on the i5. The i7 has hyperthreading (hence seeing the 8 cores) but that doesn't do enough to give it a substantial lead.

The article also shows the i5 outperforming the i7 in power consumption, which should be a deciding factor when buying a notebook.

But at the end of the day, you are comparing a notebook with a desktop, so it's a little lopsided. The iMac has a much better video card and a larger screen with a higher resolution. There is much more to a system than the CPU. On a whole, the iMac is a faster (better) machine, but not portable.

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Faster is not objective category since it always should be asked faster for what? Geekbench in 64bit mode gives ~ 8600 for Intel Core i5-2500S 2.7 GHz (4 cores) and ~9500 for Intel Core i7-2635QM 2.0 GHz (4 cores) by this numbers alone we should say Macbook Pro is faster, right?

But Geekbench only take processor, cache and RAM speed into account. What does it mean is for example encoding video in well threaded application (let's use Handbrake's h.264 engine as an example) MBP will finish around 10% faster if we abstract from i/o speed (hdd or odd)

But in a case of not so well threaded application (Adobe Photoshop for ex.) iMac's faster clock will probably gives better results.

And since iMac's HDD is a bit faster than MBP's one this will also add to a difference.

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if I try playing an HD movie Trailer on YouTube (at 480p) and capture the video area + some extra space using "Record Screen" with QuickTIme 10.1, then iMac 27 was about 70% to 80% CPU usage, while the Macbook Pro 15 was about 50% CPU usage (I saw the 8 graphs... didn't check for the average) So seems like in this case, Macbook Pro is more powerful –  動靜能量 Oct 11 '11 at 3:12
    
I'm sorry but it's hardly an objective test either since crop area/video encoded/background processes are different in those two cases. I believe you should present us with your real use cases. –  iskra Oct 11 '11 at 20:08
    
but I crop the approximate same area on both machines... I supposed I can next time go to the Apple Store and crop almost the same area as the 480p (expanded view) of the video and do a screen recording and find out the overall CPU usage for each machine –  動靜能量 Oct 12 '11 at 3:42
    
Is realtime capturing of cropped area of screen going to be you primary activity on said MacbookPro or iMac? –  iskra Oct 24 '11 at 17:03

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