over the last weeks i did much testing with the pi zero w - and my summary: ‘this is a really amazing machine’!
connected directly to my roof antenna the zero was able to handle more than 300 aircrafts in parallel while mlat was activated (~80%cpu load). since a couple of days i run it to collect and consolidate the data of my other pi2 via socat. with about 200 aircrafts in sight, dump1090 in net-mode, mysql-database active and my php-script the cpu-load is about 11%!!! moreover this little thing can run hours and hours from a small battery-pack and always runs with very low cpu-temperature.
so - everybody who runs a pi2 and is wondering what advantage a pi3 for dump1090 would be. forget about it - more than 90% of all fa-sites worldwide would easily run from a pi zero