Having used both at home, Tomato is much easier for doing standard home WiFi things. You can change wireless power levels, setup guest networks, etc easily within the UI.

Pfsense/opensense is easier when you have complicated routing needs, like multiple vlans with various split tunnels, etc.

It’s not 100% accurate, but imo if you want a short-hand you could say tomato is WiFi focused with routing support, and opensense is routing focused with WiFi support.

It’s first and foremost a WiFi router OS and it’s aimed at home users. PfSense is very much a “big guns” solution and is typically not installed directly on WiFi routers, rather it is the gateway that everything runs through.

It's pretty great for home router/wifi usage or SOHO... not as advanced/flexible as pfsense/opnsense though. I miss Tomato a lot myself, but switched to separate router/ap a few years ago, and haven't had a device that could run tomato in close to a decade now.