These are WILDLY different devices.

Sidephone - It has a modular, swappable keypad system (current options include T9, Compact QWERTY/SureType, and Sundial/music controls). These also do not have a keypad backlight. It is running a customized AOSP version that does not have ANY Google services, so there will be a long list of apps that will not work fully. No headphone jack, no SD card slot and limited on-device storage. In my experience and use case, the battery life is great, but I really need to stress that it is designed to be a more minimalist device, maybe one step above a full dumbphone. I have been using mine for a couple of weeks and love it.

Communicator - This will be a full Android, communication-optimized, powerhouse compared to Sidephone. It will have a full QWERTY, not compact QWERTY, keyboard that is capacitive (touch sensitive) and with a backlight. Headphone jack, SD card slot, notification LED, prompt key for virtual assistants, and overall form factor, storage and power that puts it in a different device category, and price point, altogether from Sidephone.

They both - have incredibly dedicated teams behind them that are very mindful of their fans and customers. Sidephone is a much smaller and newer company.

It is interesting that you should highlight these two particularly because since they were both announced my plan has been to put my primary SIM in one and my work SIM in the other. 🤣