The wire-free pick for shaded lots: Husqvarna's EPOS satellite system is built to hold position under tree cover and overcast skies where plain GPS drifts.
The cheapest credible wire-free mower. RTK satellite positioning, no boundary wire to bury — best for small, open, fairly flat lots.
Step-up i-series Navimow with better mapping. Wire-free RTK for small-to-medium open yards; wants clear sky for the GPS fix.
Lowest upfront cost of any wire-free unit. A magnetic boundary strip replaces buried wire and vision helps it cope with some shade — strong for tiny lots and fast payback.