How fast are the "Late 2013" Aluminum iMac models compared to one another? How much faster are the "Late 2013" models than the "Late 2012" models replaced?

Please note that the "Late 2012" and "Late 2013" iMac models have been discontinued. However, this Q&A still can be quite helpful to anyone buying or selling one of these systems on the used market.

In the company press release for the "Late 2013" Aluminum iMac line -- the iMac "Core i5" 2.7 21.5-Inch, "Core i5" 2.9 21.5-Inch, "Core i7" 3.1 21.5-Inch, iMac "Core i5" 3.2 27-Inch, "Core i5" 3.4 27-Inch and "Core i7" 3.5 27-Inch -- Apple repeatedly proclaims that the systems are "faster" but provides more detail regarding graphics performance.

Specifically, Apple notes that the graphics performance is "up to 40 percent faster than the previous generation" but does not mention an estimated overall speed difference.

As a result, unofficial performance information can be particularly helpful for more detail as well as greater objectivity than any company's marketing department.

Photo Credit: Apple, Inc. (21.5" & 27" Tapered Edge iMac, Left & Right, Respectively)

General Performance Overview

For a solid overview of the performance difference between the "Late 2013" Aluminum iMac models and earlier iMac systems, EveryMac.com's own Ultimate Mac Comparison makes it quick to compare side-by-side 32-bit and 64-bit Geekbench benchmark averages with all other G3 and later Macs for thousands of possible performance comparisons.

For example, the Geekbench 3.0 benchmark shows that the entry-level 27-Inch model -- the iMac "Core i5" 3.2 27-Inch -- is roughly 12% faster than the entry-level 21.5-Inch model -- the iMac "Core i5" 2.7 21.5-Inch. In turn, the discontinued high-end stock 27-Inch model -- the iMac "Core i5" 3.4 27-Inch -- is about 4% faster than the entry-level 27-Inch model. Finally, the discontinued configure-to-order iMac "Core i7" 3.5 27-Inch is 22% faster than the high-end stock 27-Inch model, 27% faster than the entry-level 27-Inch model and a whopping 42% faster than the entry-level 21.5-Inch model.

Compared to the "Late 2012" line, Geekbench 3.0 shows that the "Late 2013" systems are between a mere 1.5% and a significant 16% faster than the model each replaced:

Other Benchmarks & Real-World Test Results

Geekbench provides a convenient overview of overall performance, but other benchmarks and application tests can be helpful for a well rounded perspective.

In a pair of reviews covering the entry-level 21.5-Inch model -- the iMac "Core i5" 2.7 21.5-Inch -- and the custom configured "Ultimate" iMac "Core i7" 3.5 27-Inch models, the industry-standard Macworld tested each with a variety of benchmarks.

For the entry-level 21.5-Inch model, Macworld found results similar to Geekbench using the third-party MathematicaMark and Cinebench CPU benchmarks, but less dramatic results using the publication's own Speedmark 8 benchmark:

[In Speedmark 8], the new iMac was 9 percent faster, overall, than the entry-level iMac it replaces, and 4 percent faster than last year's step-up model, the 21.5-inch iMac with a 2.9 GHz Core i5 Ivy Bridge processor. In terms of CPU performance, the new iMac was 12 percent faster in MathematicaMark and 14 percent faster in the Cinebench CPU test than last year's iMac with its quad-core 2.7 GHz Ivy Bridge processor.

For the "Ultimate" configuration -- complete with the custom 3.5 GHz "Core i7" processor upgrade, the 4 GB NVIDIA GeForce GTX 780M graphics upgrade, and a 3 TB Fusion Drive, but the stock 8 GB of RAM (for a total cost of US$2699) -- Macworld likewise reported Speedmark 8 benchmarks similar to Geekbench:

The new CTO iMac was 6 percent faster, overall, than last year's custom iMac, a 27-inch model with a 3.4 GHz quad-core Core i7 (Ivy Bridge) processor, 1 TB Fusion Drive, 8 GB RAM, and Nvidia GeForce GT 680MX graphics with 2 GB of video RAM. The new custom iMac was 48 percent faster than last year's top of the line iMac and 57 percent faster than the new entry-level 21.5-inch iMac.

The excellent ArsTechnica also reviewed the entry-level 21.5-Inch model and reported:

Comparing this year's base model to the base models from the last two years, the story is very much the same as last year's: Haswell [Last 2013] is a performance upgrade over an Ivy Bridge [Late 2012] or Sandy Bridge [Mid-2011] CPU running at a similar clock speed, but not really so much that you'll notice for most tasks. . . [For graphics] the Iris Pro 5200 is technically an integrated GPU, but it nevertheless offers performance slightly above the dedicated GeForce GT 640M in last year's low-end iMac under both OS X and Windows 8.

The details oriented BareFeats additionally provides a variety of benchmarks and application tests that compare CPU and storage and graphics performance of the "Late 2013" iMac "Core i5" 3.4 27-Inch and iMac "Core i7" 3.5 27-Inch to each other as well as the "Late 2012" iMac "Core i7" 3.4 27-Inch and the "Mid-2010" Mac Pro "Six Core" 3.33 (Westmere).

Performance Summary

Ultimately, the "Late 2013" iMac models are notably faster overall compared to the "Late 2012" iMac models replaced, but how much faster definitely depends on the specific configuration details as well as the tasks performed.

Just among these models, for those interested primarily in performance, the configure-to-order iMac "Core i7" 3.5 27-Inch system, ideally equipped with the faster NVIDIA GeForce GTX 780M graphics card in addition to the processor upgrade, is the top choice. If you instead are looking for the best overall price-to-performance ratio -- the entry-level 27-Inch model -- the iMac "Core i5" 3.2 27-Inch -- is the best option as it costs 10% less than the standard high-end 27-Inch model -- the iMac "Core i5" 3.4 27-Inch -- but only is approximately 4% slower.

New & Used iMac Purchase Options

There are many places to purchase a used "Late 2012" or "Late 2013" iMac. However, purchasing from a quality business with years of experience in the Mac market -- and after sales support -- is the best option and will save you money and time, too.

In the US, site sponsor Adorama sells new iMac models with free shipping. Other World Computing sells used and refurb iMac models at bargain prices with free shipping, as well. Finally, if you need to sell an iMac, A+ BBB-rated Cash for Your Mac will buy your older iMac with an instant quote and prompt payment.

In the UK, site sponsor Hoxton Macs sells used iMac models with a one-year warranty and free next day delivery throughout the UK. Delivery across Europe also is available starting at just £9.99 for two-day delivery to France and Germany.

Please also see EveryMac.com's Ultimate Mac Comparison feature to dynamically compare any iMac model to any other Mac.