should i upgrade my late 2013 2.3 8Gb to a 2017 2.3 16Gb. will i see much difference in performance

Allan Jones wrote:

⚠️ NO! The 2017 2.3ghz 21.5-inch iMac is the crippled educational/institution version made for price-sensitive bulk buyers with very limited computing needs. It has a slow, laptop-class 2-core processor, not the faster 4-core processors installed in the the consumer models.

Apple released two 21.5" iMacs in 2017.

• The iMac (21.5-inch, 2017) had a 1920x1080 screen, and came with a 2.3 GHz Core i5.
• The iMac (Retina 4K, 21.5-inch, 2017) had a 4096x2304 screen, and came with a 3.0 GHz Core i5, a 3.4 GHz Core i5, or a 3.6 GHz Core i7.

"2.3 GHz" pegs the one the OP is considering as the less-desirable non-Retina model. Although benchmarks should not be taken as the final word, here are some just for amusement.

• This iMac – 1158 / 2411
• The Retina 4K model that had a Core i7 – 1360 / 4633
• A 24" M3 iMac with an 8-core GPU – 3043 / 11706

Although the M3 iMac destroys this "crippled educational/institution version" of the 2017 21.5" iMac in terms of raw CPU power, for many things, what matters is whether you have enough RAM, and a reasonably fast disk.

The 2017 21.5" iMacs came with

• A 1 TB HDD (5400 rpm notebook-type),
• A 1 TB Fusion Drive (with the same hard drive, and only 32 GB flash storage), or
• Flash storage (256 GB was the only pure flash storage option on the "crippled" models)

If the iMac in question has a 1 TB HDD or a 1 TB Fusion Drive, those are going to be performance bottlenecks. While the 32 GB SSD is a fast PCIe SSD, there is not enough of the desirable SSD "real estate" to go around … without an external SSD startup drive, performance may disappoint even for basic tasks.

Maybe. Apple never made a 2.3GHz 2013 iMac so that has to be a typo.

The faster ports, newer WiFi standards, and extra RAM will boost performance in their own ways, but the CPU/GPU in the 2.3GHz 2017 dual-core 21.5" iMac is underpowered for its year and would only be a meaningful upgrade over the Early-2013 3.3GHz i3 model. I would not recommend the 2017 2.3GHz model if you currently have an i5 or an i7 CPU.

A better question: Why are you considering an upgrade?

For example, if startup is too slow and your current iMac has an HDD you may wish to consider instead using an external SSD.

⚠️ NO! The 2017 2.3ghz 21.5-inch iMac is the crippled educational/institution version made for price-sensitive bulk buyers with very limited computing needs. It has a slow, laptop-class 2-core processor, not the faster 4-core processors installed in the the consumer models.

Like padams35, I do not see a 2.3 ghz Late 2013 iMac listed. These are benchmark scores of the Late 2013 21.5 iMacs compared the the 2017 "limp-along" version:

The 2017 would be going backwards! We see many complaints here from people who mistakenly bought the edu-iMacs.

You may see some performance increase, but that all depends upon the condition of this 2017 iMac. For me, I wouldn't do it, as it's near its end of life as far as Apple Support is concerned. You may run into issues with certain apps, as some software vendors (Adobe and Microsoft come to mind) may not offer updated apps for that 2017 iMac, as they tend to support only the last 3 MacOS versions. Also, your 2013 iMac may be running 32 bit apps (don't know this for sure, as I haven't looked it up) which would not be supported by the 2017 iMac.

And, for sure, I would never advise purchasing a used Mac from anywhere other than authorized Apple resellers or Apple. All too often these Macs are not prepared properly for resale, and end up being (very) expensive doorstops.

Just my $0.02 worth.