I think it’s a bit safer than WhatsApp security wise, but won’t make any difference for general people like us whatever the usage. I just got fed up with having two different message platforms running parallel, so removed Telegram as most were using WA really.
Me and o/h have two four-way group chats set up on WA for the two couples we are very friendly with (A+L & C+B) they have never met each other though. Both chats can end up a bit risqué but nothing that would be mega embarrassing.
However there is the odd thing I would say directly to C that I wouldn’t say to the others and using the other app would help keep this more separate. Nothing that would cause a problem or argument if discovered, but stuff the others may not be overly interested in, I do go into to much detail sometimes.