both should work as a basic dimmer with smart things, but you can’t change the settings or use advanced features without a specific device type (or a secondary controller).
The major differences include;
212 is the latest version 211 is older.
how they cope with dimming the 212 supports both leading edge and trailing edge and automatically selects the best. the 211 doesn’t (think it is trailing edge only, can’t remeber). This just means you can use more different tyeps of bulb withous flickering.
the 212 supports energy metering the 211 doesn’t,
also the minimum load is 25W for the 211 and 50w minimum for the 212. (but you can buy a bypass to use a smaller load)
The 212 uses the more advanced Zwave plus the 211 uses normal zwave (you can mix and match)
I have the 211s across my house, and had to change options on them using a USB Zwave controller, as I am using toggle rather than momentary switches.
The price is the same in most places so the trade off is really if you want energy metering or more choice of bulb go with the 212
if you want to use larger loads or you want to use smaller loads without extra cost get the 211.