We have an older LG smart TV and can only get Spark Rural WiFi. Are we better off to get Chromecast Ultra or the 2018 one?
Is it a 4k TV? Do you subscribe to any 4k streaming services? If no to either, then get the regular. If yes to both, then get the Ultra.
Put another way, what problem are you trying to solve here? Are you looking to start using a streaming service, or replace/supplement an existing means of streaming?
Most streaming services don't need a whole lot of bandwidth (Netflix recommends around 25mbps for 4k streaming), but they will certainly chew through it if you are on a capped connection.