What can the 2019 iMac do that the 2011 iMac can't

FYI, your fan is running at full speed by default because you need to add a heat sensor to your 3rd-party SSD. If you do high-intensity tasks you may want to consider doing that versus using software to always slow down your fan:

https://eshop.macsales.com/item/OWC/DIDIMACHDD11/

Newer iMacs are glued/sealed and very difficult to upgrade the hard drive. The RAM can still be upgraded though.

Being able to run the current/supported version of macOS though is a pretty compelling reason to upgrade. That's the only way to get the latest security and Safari browser updates. Once your macOS is more than one whole version behind it's no longer officially supported, so when the new version of macOS comes out this fall that would definitely be an issue to consider.

Ultimately though, if it's still running great for you that's the most important thing.

A 2019 iMac will have at least a 1 year warranty, and up to 4 years if you spring for AppleCare coverage.

FWIW, I believe AppleCare extends warranties to three years, not up to four.

AppleCare+ - Mac - Apple

A 2011 cannot upgrade the OS beyond High Sierra 10.13.6 which means Apple will likely discontinue security updates sooner than later. By the way, I also have a 2011 iMac, however I realize that I will likely need to replace it in the next year or so. When it comes to technology, you cannot stick your head in a hole forever, it eventually catches up to you and you must upgrade. Sometimes the longer you wait the more painful upgrading can be.

FWIW, if you actually sit down and work with a 27", 2019 iMac with an

SSD (no Fusion or HDD), your 2011 will seem like a slug.

Just some basic Geekbench numbers comparing a maxed out 2011

with a base 2019:

single core score. multicore score

Maxed out 2011. 3514 11203

Base 2019. 5247 21712

If you don't have the highest performance 2011 that was offered,

the difference will be even greater.

Add to that, the much higher speed USB3 that is available vs. the USB2

or even Firewire800. Then there is also Thunderbolt 3.....

A 2019 iMac will have at least a 1 year warranty, and up to 4 years if you spring for AppleCare coverage. Your 2011 iMac is rapidly approaching Apple's worldwide obsolete list which means no service or parts from Apple or Apple Authorized Service Centers. At eight years old, and without warning, something other than your SSD may fail, and you will be up that famous creek without oars.

2011 iMacs have been considered obsolete by Apple for about 2 years now. Also, AppleCare extends the original 1 year warranty an additional 2 years so if they purchase AppleCare they will have a total of 3 years, not 4.

Yes, you can use the old computer's Time Machine backup to setup your new computer. The most simple method is to connect the Time Machine drive to the new computer prior to turning it on for the first time using a USB cable. Why USB, easy it is the most fastest, most reliable method. Try other methods (Wi-Fi, ethernet, etc..) it likely won't work.

When you turn on the new computer it will launch Setup Assistant, SA will get to a point where it asks if your migrating from another Mac, select yes and then follow the on-screen menus and you're done. It really is that easy.

You may have apps that may be either too old to migrate or some developers (Microsoft and Adobe almost always) don't allow their software to be migrated, this means you will have to re-install or upgrade.

Good luck with the new Mac.

Yes, you are correct.