iMac 27" vs iMac 24" M3 - Memory question

Have you actually been using that 128GB RAM? (serious question, not a joke or snark)

The entire Apple Silicon architecture is very different from Intel, and other than finding good benchmark studies it's difficult to tell where the crossover may be on RAM in one vs. the other ... and RAM is 20% faster on Apple Silicon than on Intel.

I do photography & video on i5, i7 & i9 iMacs with 16-24 GB RAM and I have never run into any difficulties with Final Cut, Photoshop, Lightroom, CaptureOne, Davinci Resolve, Screenflow and similar apps. The machines all have either 7200rpm WD Black HDDs and/or Samsung 870 EVO SSDs and all are on SATA connections.

Personally, I have no reason to think that 24GB RAM on an M3 Mac would be a downgrade in performance. But you may have higher requirements than I do. If you have the need and want a high-end workstation, it would be better to consider a Mac Studio than an iMac.

https://browser.geekbench.com/mac-benchmarks

Various benchmarks do seem to show significantly faster performance with the M3 iMac versus 2020 iMac 8 core Intel. But I can't tell how much memory is used for those benchmarks, I am guessing it is probably an equal amount. Losing 80% of your memory also concerns me. When your Mac runs out of memory, which it certainly will with Adobe video and image processing tools, it has to start paging to disk. Which should be reasonably fast with a fast internal SSD, but having more memory is always much faster. I think I agree with the others about paying attention to the memory that the machine comes with. And if there is indeed lots of disk paging going on, if the Mac starts running low on disk space that almost immediately causes the entire machine to slow to a crawl with rainbow balls, etc. I have seen hundreds of GB gets used for temporary space on my daughter's Mac which is used only with Adobe Lightroom and Photoshop, she does not even do any video processing, no doubt that is more demanding. I would be cautious about going with a lower end iMac with not enough memory from the get go.

The M3 will be faster than the 2020 Intel iMac.

As for the memory, you may take a hit there as 24 is a considerable downgrade from 128 even if the M3 memory management is more efficient.

If you use the Mac for your income you might consider the M2 Studio with either 64 GB RAM max or 128 GB RAM max with a 3rd party monitor. Of course the cost wood be much more expensive.

Another option is the Mac Mini wit 32 GB RAM and an 3rd party monitor.

The M3 would be more than sufficient for photo editing but don't know about video. I don't do any video editing so have no feel for what might be better.

Just some food for thought and I hope I haven't confused your any more.

I'd say quite a bit.

You are not only going from 128GB to 24, ut you are also going from a high end CPU to an entry level one.

As good as the M3 is, you will experience significant performance downgrade if you tend to have a ton of images and videos opened and processing at the same time.

The new iMacs are entry level computers for general low to mid end use. They are not meant as big powerful workhorses for Video rendering and large high quality image processing.

If you want something more on-par with the 27" iMac, look at a Mac Studio with a good display.

You can bump that one up to much more RAM and with the better M2 Max CPU you will get much more comparable experience.

+1 on Phil0124 recommendations