Main difference between the two is USB-C on the S3423DWC for an extra $43.89, but only does 100Hz instead of 144Hz.
S3423DWC here: https://www.dell.com/en-au/shop/dell-34-curved-usb-c-monitor…
Similar recent deals: https://www.ozbargain.com.au/node/781289 & https://www.ozbargain.com.au/node/775521
S3423DWC has speaker whilst S3422DWG no speaker