Our company mandated a change on company devices to Signal  which prompted me to do a bit of reading on it.

The only real difference that I could see was that the PIN system stopped someone stealing your Signal account and spoofing you (by doing the SMS 2FA swindle via unauthorised SIM card swap that is common in the UK but not so much in NZ). I found the PIN reminder system to be less than seamless and I'm sure it has been disabled on all company devices by now.

The end to end encryption of messages is a staple of the message app segment now days. 

I can see why they would drop SMS - it removes the chance of a message mistakenly being sent un-encrypted via SMS - a slip-up like that could be catastrophic for a Cartel.