Advice needed- will M3 iMac be better than my current iMac?

It will be a HUGE upgrade in performance unless your current machine already has a SSD as its startup drive. Forget what you think you know about CPUs, GPUs and RAM. The M series of Macs are in a completely different league than the Intel machine. You would be trying to compare Wilbur & Orville's original airplane with a F22 Raptor. About all they have in common is they are designed to fly.

Hello.

As everyone has said, it is a huge upgrade to the latest iMac. I personally have seen the massive jump from Intel to the M-series chip. It has been night and day for me. And also, with the new iMac you can choose the color, basically the colors of the rainbow. It has a way different design than your current iMac, with it more looking like an iPad on a stand with more color and thin borders.

If you haven’t bought the new iMac already, there is another cost-effective option. You could get a Mac mini with M2 chip, but still having the experience of the M-series chips. It itself is half the price of the iMac and you can get a display for very cheap, so comparatively, it is more cost effective. But, if you want an amazing all-in-one (meaning chip & display), then the new iMac is a great choice.

Hope this helps.

I have the same i7 iMac with factory SSD option and it remains very fast. All M-series Mac have SSDs.

Maybe some benchmark data will help. From the MacTracker database, which has not yet been updated to show the new M3 iMacs:

I suspect the M3 willl be faster.

My caveat would be ports. The entry-level M-series iMac has too few ports. I cannot recommend anything less than the four-port model. IF you need a gob of ports, you are left with the more expensive Mac Studio that still needs a monitor and input devices.

The new iMacs are far more powerful and quicker than your 2015. As far as RAM unless you are doing very heavy duty computing, 3D graphics such as CAD/CAM, gaming etc. chances are 16GB of RAM is much more than you need. I have a 2020 27" iMac with a 2TB SSD and 40 GB of RAM, this machine is way overkill for my needs. My next machine will likely have the same amount of storage however I'm considering 8GB of RAM, 16 at the maximum.

The only downside that I see is the smaller display, if that is a show stopper for you then buy a Mac mini or a Mac Studio and add the display you want. You are not limited by having to buy another iMac. You can also get yourself a MBA or MBP and install a larger display again, no downside.

Instead of seeing limitations in the current iMac series, look at as an opportunity to look at all the different possibilities available to you. The new Macs are really really nice machines and in every capability far outweigh your almost 10 year old iMac.

I recently priced out some iMac models vs. the macMini with a 27" Apple Studio Display. The macMini + Display combo came in a few hundred $ less than the comparable iMac (and it's a 27" display, not a 24" iMac). You could do even better with a 3rd party display (at least on cost, not necessarily on display quality).

There is lots to be said for the Mini. Just be aware that like the other Mac models, you cannot upgrade RAM or SSD later.

I read at least one article by ZDNET that said something about not being able to run some windows software on the mini. Not sure what that’s about.

ZDNET:

The cases where I'd recommend against it are:

• The difference in storage speed really will impact you: As mentioned above, if you frequently open or save massive files, consider either external storage options or an upgraded storage tier before purchasing. 
• You absolutely need access to software that's not available for MacOS: Unlike older Intel-based Macs, the M2 (like the M1 before it) doesn't offer an easy way to run Windows-based software. This means if a Windows-only title is vital to your work or play, you're out of luck. 
• You're a gamer: Macs are still bad at serious gaming, despite the massive performance improvements brought on by Apple silicon. The lack of a discrete GPU, poor MacOS support among game devs, and other technical factors mean this is just not the system to buy if you plan on serious gaming. 

I'm curious to hear why you said that. I am in the same boat as the OP. I have a late 2015 27" iMac that may have some hardware issues and I am beginning to look at new iMacs. The first thing that jumped out at me is the smaller screen and the inability to add RAM. What are your thoughts about those limitations? Other options? Thanks in advance.

You know, that is exactly what I was thinking. Unbundling the processor from the display like the old days before I got an iMac.

Would be cool to find an older 27” display in good shape and connect a Mac Mini to it.

Any downsides to a Mac Mini? I assume it would compare well with my late 2015 iMac? No idea about RAM, etc on the Mac Minis.

No downsides to them at all, I'm considering one as my next Mac. By the way, Samsung has a number of displays that will work, just select one that suits your needs and you're good to go. You can use your iMac's keyboard and mouse and all of your peripherals.

Your welcome.

By the way, when replying to a message on these forums please click "Reply" to the post you are replying to, otherwise it looks like you are talking to yourself.

Hmmmmm. That is fascinating. I’ll do some checking. Any Samsung models that you think would be a good fit?

No idea, you need to do your own research on that.

Found several sites with lists. Thanks.

Unlike the Intel versions - which even had bootcamp - there is no easy way to run Intel based windows software on Apple Silicon.

So, do you need to run Windows programs?