I have a garmin edge 800 at the moment, bug am considering changing to the newer edge 520. Does anyone have any thoughts as to if there are enough benefits?

What do you use it for?
Just got a 520 and it’s great compared to a 510. Base maps make folloiwng a breadcrumb trail easier.
Maps are zoomable but you can’t pan
Maps limited to 90mb
No navigation

None of those are issues for me as I plan ahead, download a local map (tablet using usb-otg) and follow courses rather than need turn by turn nav.

I prefer keys to touch screen.

Not sure compared to the 800 but if you need nav or powerful mapping, mayne not.