Hi Christine, what a legacy from your Grandmother. My condolences on her passing.
When it comes to these two machines, I can tell you that the Innovis-4000D is the more modern of the two. They're both discontinued, so finding sites that allow you to side-by-side compare them is unlikely.
But I'll tell you the areas that embroiderers usually use to compare machines: speed, LCD screen, embroidery area, and ability to use designs from outside sources.
You are right that many people upgrade mostly for the sewing area. The Brother PC-8500 has a 5x7 embroidery area (even if you put a bigger hoop on, the design area remains the same), while the 4000D has a 12x7 embroidery area.
Another reason to upgrade is the way that designs are transferred to the machine. The PC-8500 uses embroidery cards and a specialized card writer box. That technology is aging and the manufacturer has not continued to support it with updates to work on Windows 11. The last computer I was able to use the PED-Basic card writer software on was running (I think) Windows 8. You could replace the box and card with a product like the Ultimate Box if you wind up needing to use a new computer for embroidery. The 4000D can also use a card, but has the added capability of recognizing USBs for design transfer, which I think will extend its life beyond that of the 8500.
The larger LCD screen is also a difference between the two.
The manuals for both machines are available online; if there are particular things you want to compare, I suggest comparing the information in the manuals.
Best wishes!
Christine M.
I have a PC-8500 Machine that my grandmother sold to me, when she upgraded to an Innov-is 4000D. My Grandmother recently passed away at the age of 100! I am trying to find something comparing the machines, to see which one I should keep and which one to sell.... Is there any site that compares the two?
Also with the PC-8500 is the 5"X7" hoop the largest you can use? Even then some designs I have downloaded to the card via Ped Basic say they are too large for the machine. I guess that would be my main reason for upgrading?